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

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

Use the pin number rather than the hybrid pin number + name.

BWCT boards uses two different SPI flash chips
check for both status codes

Since we're about to set ST_RTMR to 1 to increase the accuracy of the
CRTR register to be 1/32768th of a second in init, we don't need to do
it here.

MFp4: Differences in flash part for bwct. need a more generic way to cope.

MFp4:

Massive update. The highlights:
o dramatically cut memory usage by writing better, less intertwingled
code.
o implement booting off mmc/sd cards (sd only tested one at the moment)
o start to split out board specific stuff for boot2.

MFp4:
Remove obsolete files in list
Add spi flash reading routines