Remove unnecessary NULL check before kvfree() reported by
Coccinelle/coccicheck and the semantic patch at
scripts/coccinelle/free/ifnullfree.cocci.
Signed-off-by: Chen Ni <nichen@iscas.ac.cn> Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Carlos Maiolino <cem@kernel.org>