lib/genalloc.c: check result of devres_alloc()

devm_gen_pool_create() calls devres_alloc() and dereferences its result
without checking whether devres_alloc() succeeded. Check for error and
bail out if it happened.

Coverity-id 1016493.

Signed-off-by: Jan Kara <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

lib/genalloc.c

···
 	struct gen_pool **ptr, *pool;
 
 	ptr = devres_alloc(devm_gen_pool_release, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return NULL;
 
 	pool = gen_pool_create(min_alloc_order, nid);
 	if (pool) {