drivers/intel/gma/opregion.c: Re-add lost log message

Commit 926949d64c (drivers/intel/gma:
Restructure IGD opregion init code) accidentally dropped this print
statement. As it can be useful for debugging purposes, add it back.

Change-Id: Iebd9e02bccc77538c0eed1e549294408586322f2
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/55567
Reviewed-by: Meera Ravindranath <meera.ravindranath@intel.corp-partner.google.com>
Reviewed-by: Subrata Banik <subrata.banik@intel.com>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/drivers/intel/gma/opregion.c

@@ -251,6 +251,7 @@ static enum cb_err find_vbt_location(struct region_device *rdev)
 		return CB_SUCCESS;
 	}
 
+	printk(BIOS_ERR, "GMA: VBT couldn't be found\n");
 	return CB_ERR;
 }