[IPSEC]: Fix crypto_alloc_comp error checking

The function crypto_alloc_comp returns an errno instead of NULL
to indicate error.  So it needs to be tested with IS_ERR.

This is based on a patch by Vicenç Beltran Querol.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/ipcomp.c b/net/ipv4/ipcomp.c
index ca1b5fd..2c44a94 100644
--- a/net/ipv4/ipcomp.c
+++ b/net/ipv4/ipcomp.c
@@ -16,6 +16,7 @@
 #include <linux/module.h>
 #include <asm/semaphore.h>
 #include <linux/crypto.h>
+#include <linux/err.h>
 #include <linux/pfkeyv2.h>
 #include <linux/percpu.h>
 #include <linux/smp.h>
@@ -344,7 +345,7 @@
 	for_each_possible_cpu(cpu) {
 		struct crypto_comp *tfm = crypto_alloc_comp(alg_name, 0,
 							    CRYPTO_ALG_ASYNC);
-		if (!tfm)
+		if (IS_ERR(tfm))
 			goto error;
 		*per_cpu_ptr(tfms, cpu) = tfm;
 	}