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

Create a generic way to support multiple boards within an
arm platform. Add all the atmel boards to the ATMEL kernel for
testing purposes. Until boot loader arg parsing of baord type
is done, this won't actually be able to do the runtime selection.

Start to make it easier to add AT91RM9200 based boards:
o Copy kb920x_machdep.c to at91_machdep.c
o Move board_init to new board_kb920x.c
o rename ramsize to at91_ramsize and make it accessible to board_* files.
o Delete files.kb920x. We can do this selection with the new boards.
o Add a stub for the tsc4370 board init, which will be added in
a future commit.
o Add new 'devices' at91_board_kb920x and at91_board_tsc4370. More are
needed and will be added in future commits.

Reviewed by: stass, cognet