mainboard/google/reef: add baseboard memory configuration
Move the current memory configuration implementation to the baseboard
area such that other variants can leverage it. The swizzle config
is exported as a global to allow duplicate swizzles to use the same
structure while still allowing different memory SKUs.
BUG=chrome-os-partner:56677
Change-Id: I57201118053051c01f0e3f164ab4bbaf650b892b
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/16430
Tested-by: build bot (Jenkins)
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>