mb/google/fatcat: Create francka variant

mb/google/fatcat: Create francka variant

Create the francka variant of the fatcat reference board.

BUG=b:370666276
TEST=util/abuild/abuild -p none -t google/fatcat -x -a
make sure the build includes GOOGLE_FRANCKA

Change-Id: I372f445f7007d0d33020545a8febbce27c260e41
Signed-off-by: Ian Feng <ian_feng@compal.corp-partner.google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/84769
Reviewed-by: Dtrain Hsu <dtrain_hsu@compal.corp-partner.google.com>
Reviewed-by: Amanda Hwang <amanda_hwang@compal.corp-partner.google.com>
Reviewed-by: Pranava Y N <pranavayn@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>