pit: Add a "pit" mainboard which is mostly a copy of "snow".

This change adds a pit mainboard which is mostly a copy of snow, except that
mentions of the 5250 were replaced with the 5420, and mentions of snow were
replaced with pit.

Change-Id: I8eb0ce379eb2fa353bb88d5656a0c5e2290afbf0
Signed-off-by: Gabe Black <gabeblack@chromium.org>
Reviewed-on: http://review.coreboot.org/3646
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
10 files changed