crypto: lib/mpi - Fix an "Uninitialized scalar variable" issue

The "err" variable may be returned without an initialized value.

Fixes: 8e3a67f2 ("crypto: lib/mpi - Add error checks to extension")
Signed-off-by: Qianqiang Liu <qianqiang.liu@163.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

lib/crypto/mpi/mpi-mul.c

@@ -21,7 +21,7 @@ int mpi_mul(MPI w, MPI u, MPI v)
 	int usign, vsign, sign_product;
 	int assign_wp = 0;
 	mpi_ptr_t tmp_limb = NULL;
-	int err;
+	int err = 0;
 
 	if (u->nlimbs < v->nlimbs) {
 		/* Swap U and V. */