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

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

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

o uses bus accessor macros to read values from ivar so no more values
are referenced directly from ivar pointer. It's to do like what other
buses do. [1]
o changes exported prototypes. It doesn't use struct siba_* structures
anymore that instead of it it uses only device_t.
o removes duplicate code and debug messages.
o style(9)

Pointed out by: imp [1]

supports SPROM rev8 informations properly which are used to support
low-power PHY of bwn(4) and LDO voltage adjustments.

Adds siba_bwn module which is used with bwn(4). Main purpose of this
module is to distinguish parts of Silicon Backplane and of Broadcom
Wireless.

Support for the siba bus found in many broadcom products.

Submitted by: bms@
Obtained from: p4 mips branch