Add the include for size_t.
Fixes compilation error on source files that do not include it.
Change-Id: Ic752886d94db18de89b8b8a5e70cf03965aeb5c3
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/31922
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>