BugLink: https://bugs.launchpad.net/bugs/1858489

[ Upstream commit f31a8969 ]

kmem_cache_destroy(NULL) is safe, so removes NULL check before
freeing the mem. This patch also fix ifnullfree.cocci warnings.
Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
Signed-off-by: David Teigland <teigland@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>