Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

MFC r257064:

Add an OFW SPI compatible bus. Fix the spibus probe to return
BUS_PROBE_GENERIC and not BUS_PROBE_SPECIFIC (0) so the OFW SPI bus can
attach when enabled. Export the spibus devclass_t and driver_t
declarations.

Submitted by: ray
Approved by: adrian (mentor)

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

Replace `inline static' by `static inline'.

If I interpret the C standard correctly, the storage specifier should be
placed before the inline keyword. While at it, replace __inline by
inline in the files affected.

Fix comments.

MFp4:
Initial spibus support. Seems to be OK, but needs some polish.

# someone should write a bit-bang spi parallel port interface :-)