MFC r279368, r280772, r280848:

Allow creating subclass of FDT simplebus

Make simplebus a base class of ofwbus.

Fix bug in xrefinfo_find() for 64-bit platforms

MFC r270953, r270958, r270960, r271190, r271199, r271202:

Create a mechanism for looking up a device_t associated with an ofw/fdt
xref handle, and for registering that association. Also use the same data
for faster translations between node and xref handles.

Add OF_xref_from_device() so that there's no need to have an intermediate
call to ofw_bus_get_node() to lookup info that's already in the xreflist.

When registering an association between a device and an xref phandle, create
an entry in the xref list if one doesn't already exist for the given handle.

MFC r270945:

Rename OF_xref_phandle() to OF_node_from_xref() and add a new function
that provides the inverse translation, OF_xref_from_node().

MFC r256932, r256938, r256966, r256953, r256967, r256969, r257015:

Add a new function (OF_getencprop()) that undoes the transformation applied
by encode-int. Specifically, it takes a set of 32-bit cell values and
changes them to host byte order. Most non-string instances of OF_getprop()
should be using this function, which is a no-op on big-endian platforms.

Use the new function all over the place.

MFC: r256932, r256938, r256953

r256932:
Add a new function (OF_getencprop()) that undoes the transformation applied
by encode-int. Specifically, it takes a set of 32-bit cell values and
changes them to host byte order. Most non-string instances of OF_getprop()
should be using this function, which is a no-op on big-endian platforms.

r256938:
A few other common cases for encode-int decoding: OF_getencprop_alloc()
and OF_searchencprop(). I thought about using the element size parameter
to OF_getprop_alloc() to do endian-switching automatically, but it breaks
use with structs and a *lot* of FDT code (which can hopefully be moved to
these new APIs).

r256953:
Fix build.

MFC r279368, r280772, r280848:

Allow creating subclass of FDT simplebus

Make simplebus a base class of ofwbus.

Fix bug in xrefinfo_find() for 64-bit platforms

MFC r270953, r270958, r270960, r271190, r271199, r271202:

Create a mechanism for looking up a device_t associated with an ofw/fdt
xref handle, and for registering that association. Also use the same data
for faster translations between node and xref handles.

Add OF_xref_from_device() so that there's no need to have an intermediate
call to ofw_bus_get_node() to lookup info that's already in the xreflist.

When registering an association between a device and an xref phandle, create
an entry in the xref list if one doesn't already exist for the given handle.

MFC r270945:

Rename OF_xref_phandle() to OF_node_from_xref() and add a new function
that provides the inverse translation, OF_xref_from_node().

MFC r256932, r256938, r256966, r256953, r256967, r256969, r257015:

Add a new function (OF_getencprop()) that undoes the transformation applied
by encode-int. Specifically, it takes a set of 32-bit cell values and
changes them to host byte order. Most non-string instances of OF_getprop()
should be using this function, which is a no-op on big-endian platforms.

Use the new function all over the place.

MFC: r256932, r256938, r256953

r256932:
Add a new function (OF_getencprop()) that undoes the transformation applied
by encode-int. Specifically, it takes a set of 32-bit cell values and
changes them to host byte order. Most non-string instances of OF_getprop()
should be using this function, which is a no-op on big-endian platforms.

r256938:
A few other common cases for encode-int decoding: OF_getencprop_alloc()
and OF_searchencprop(). I thought about using the element size parameter
to OF_getprop_alloc() to do endian-switching automatically, but it breaks
use with structs and a *lot* of FDT code (which can hopefully be moved to
these new APIs).

r256953:
Fix build.