qede_build_skb() assumes build_skb() always works and goes straight
to skb_reserve(). However, build_skb() can fail under memory pressure.
This results in a kernel panic because the skb to reserve is NULL.
Add a check in case build_skb() failed to allocate and return NULL.
The NULL return is handled correctly in callers to qede_build_skb().
Fixes: 8a8633978b ("qede: Add build_skb() support.")
Signed-off-by: Jamie Bainbridge <jamie.bainbridge@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
4e910dbe36