Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Add OF_prop_free function as a counterpart for OF_*prop_alloc

- Introduce new OF API function OF_prop_free to free memory allocated by
OF_getprop_alloc and OF_getencprop_alloc. Current code just calls free(9)
with M_OFWPROP memory class which assumes knowledge about OF_*prop_alloc
functions' internals and leads to unneccessary code coupling

- Convert some of the free(..., M_OFWPROP) instances to OF_prop_free

Files affected by this commit are the ones I was able to test on real
hardware. The rest of free(..., M_OFWPROP) instances will be handled with
idividual maintainers

Reviewed by: andrew
Differential Revision: https://reviews.freebsd.org/D6315

Fix whitespace glitch from prior comit.

Reimplement fdt_clock_register_provider() correctly. It turns out you
can't use OF_xref_from_device() to implement the function that registers
the xref association with the device.

Pointy hat: ian
Submitted by: loos

Use OF_xref_from_device(), not OF_xref_from_node(). Also, use bzero()
rather than memset().

Create an interface for drivers to enable or disable their clocks as listed
in the clocks=<...> properties of their FDT data. The clock properties
consist of 2-cell tuples, each containing a clock device node reference and
a clock number. A clock device driver can register itself as providing
this interface, then other drivers can turn the FDT clock node reference
into the corresponding device_t so that they can use the interface to query
and manipulate their clocks.

This provides convenience functions to enable or disable all the clocks
listed in the properties for a device, so most drivers will be able to
manage their clocks with a single call to fdt_clock_enable_all(dev).