mb/google/brask/variants/moli: remove mainboard_vbt_filename in ramstage

mainboard_vbt_filename() is to decide which VBT to return,
but moli only has one VBT, so it doesn't need this function.

BUG=b:234521809
TEST=emerge-brask coreboot.

Signed-off-by: Raihow Shi <raihow_shi@wistron.corp-partner.google.com>
Change-Id: Ia9c1495c8cb7bf7b47d9c616891a791a32b9d805
Reviewed-on: https://review.coreboot.org/c/coreboot/+/64848
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/google/brya/variants/moli/ramstage.c

@@ -32,11 +32,6 @@ const struct psys_config psys_config = {
 	.bj_volts_mv = 19500
 };
 
-const char *mainboard_vbt_filename(void)
-{
-	return "vbt-moli.bin";
-}
-
 void variant_devtree_update(void)
 {
 	size_t total_entries = ARRAY_SIZE(limits);