mm/zswap: fix passing zero to 'PTR_ERR' warning

Fix smatch warning:

  mm/zswap.c:425 zswap_cpu_comp_prepare() warn: passing zero to 'PTR_ERR'

crypto_alloc_comp() never return NULL, use IS_ERR instead of
IS_ERR_OR_NULL to fix this.

Link: https://lkml.kernel.org/r/20201031055615.28080-1-yuehaibing@huawei.com
Fixes: f1c54846 ("zswap: dynamic pool creation")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/zswap.c

@@ -421,7 +421,7 @@ static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
 		return 0;
 
 	tfm = crypto_alloc_comp(pool->tfm_name, 0, 0);
-	if (IS_ERR_OR_NULL(tfm)) {
+	if (IS_ERR(tfm)) {
 		pr_err("could not alloc crypto comp %s : %ld\n",
 		       pool->tfm_name, PTR_ERR(tfm));
 		return -ENOMEM;