drivers/intel/fsp1_1: Fix vbt_len type

Type of vbt_len should be size_t, change to fix compiler error

Change-Id: I22798fa0edb98fcb9acc1b2dd52f34a61bc511e9
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/27224
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
1 file changed