In a situation where memory allocation fails, an invalid buffer address
is stored. When this descriptor is used again, the system panics in the
build_skb() function when accessing memory.

Fixes: 7ea6cd16 ("lantiq: net: fix duplicated skb in rx descriptor ring")
Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>