libflashrom.h: Add missing includes

<stddef.h> for `size_t` and <sys/types.h> for `off_t`.

Change-Id: Ifc84dfe2a06633321d0abd364bdea1216925a779
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/c/30153
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: David Hendricks <david.hendricks@gmail.com>
1 file changed