crypto/asymmetric_keys: pkcs7_key_type needs module.h

This driver builds off of the tristate CONFIG_PKCS7_TEST_KEY and calls
module_init and module_exit. So it should explicitly include module.h
to avoid compile breakage during header shuffles done in the future.

Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: linux-crypto@vger.kernel.org
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

crypto/asymmetric_keys/pkcs7_key_type.c

@@ -12,6 +12,7 @@
 #define pr_fmt(fmt) "PKCS7key: "fmt
 #include <linux/key.h>
 #include <linux/err.h>
+#include <linux/module.h>
 #include <linux/key-type.h>
 #include <crypto/pkcs7.h>
 #include <keys/user-type.h>