mb/google/poppy/variants/nami: Add memory detection logic

Alkali will use LPDDR3, so need to have Nami support both
DDR4 and LPDDR3.  We do this with the PCH_MEM_CONFIG4 GPIO.

BUG=b:73514687
BRANCH=None
TEST=None

Change-Id: Ife6740ce0e8fe109ded7b954134171ba91895628
Signed-off-by: Shelley Chen <shchen@chromium.org>
Reviewed-on: https://review.coreboot.org/25000
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
3 files changed