x4x: make preallocated IGD memory a cmos option

This allows to set the preallocated memory for the IGD on x4x
using a cmos option.
If no cmos option is found a default value of 64M is used.

TESTED most options on ga-g41m-es2l with 2G dimm in one slot and 2x2G.
352M also works in contrast with gm45 where it is known to cause issues
with certain ram combinations.

Change-Id: I9051d080be82f6dfab37d353252e29b2ed1fca7f
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/15492
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
1 file changed