drivers/pc80: Rework normal / fallback selector code

Per IRC and Gerrit discussion, the normal / fallback
selector code is a rather weak spot in coreboot, and
did not function correctly for certain use cases.

Rework the selector to more clearly indicate proper
operation, and also remove dead code.  Also tentatively
abandon use of RTC bit 385; a follow-up patch will
remove said bit from all affected mainboards.

The correct operation of the fallback code selector
approximates that of a power line recloser, with
a user option to attempt normal boot that can be
cleared by firmware, but never set by firmware.
Additionally, if cleared by user, the fallback
path should always be used on the next reboot.

Change-Id: I753ae9f0710c524875a85354ac2547df0c305569
Signed-off-by: Timothy Pearson <tpearson@raptorengineeringinc.com>
Reviewed-on: http://review.coreboot.org/12289
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
4 files changed