allocate_flower_entry: should check for null deref

[ Upstream commit bb1320834b8a80c6ac2697ab418d066981ea08ba ]

allocate_flower_entry does not check for allocation success, but tries
to deref the result. I only moved the spin_lock under null check, because
 the caller is checking allocation's status at line 652.

Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>