staging:rtl8712: avoid skb_clone after skb allocation fail

The skb allocated when out of memory is likely to be discarded
during subsequent processing.

Signed-off-by: Ivan Safonov <insafonov@gmail.com>
Link: https://lore.kernel.org/r/20200531110548.9318-1-insafonov@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>