staging: ccree: handle end of sg list gracefully

If we are asked for number of entries of an offset bigger than the
sg list we should not crash.

Cc: stable@vger.kernel.org
Signed-off-by: NGilad Ben-Yossef <gilad@benyossef.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/ccree/ssi_buffer_mgr.c

@@ -94,7 +94,7 @@ static unsigned int cc_get_sgl_nents(struct device *dev,
 {
 	unsigned int nents = 0;
 
-	while (nbytes) {
+	while (nbytes && sg_list) {
 		if (sg_list->length) {
 			nents++;
 			/* get the number of bytes in the last entry */