blspec: fix erroneus free in entry_is_of_compatible()
Whenever of_unflatten_dtb() encountered an error it already released the memory
before returning the error code. Make this apparent by setting the pointer to
NULL to avoid an erroneus free.
Signed-off-by: Ulrich Ölmann <u.oelmann@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>