mb/google/rex/var/screebo: Add initial setup for gpio config

add the initial gpio configuration for screebo initial variant

BUG=b:276814951
TEST=emerge-rex coreboot

Signed-off-by: Kun Liu <liukun11@huaqin.corp-partner.google.com>
Change-Id: Ib96e03f47bc1d6e5628ae459c3e1eb4dc18849c7
Reviewed-on: https://review.coreboot.org/c/coreboot/+/74475
Reviewed-by: YH Lin <yueherngl@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Subrata Banik <subratabanik@google.com>