tests: Silence compiler warnings from test-base64

Use typecasting to match the base64_{encode,decode}() function prototype
for signed/unsigned char buffer.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>

tests/test-base64.c

@@ -26,9 +26,9 @@ int main(int argc, char *argv[])
 		return -1;
 
 	if (strcmp(argv[1], "encode") == 0)
-		e = base64_encode(buf, len, &elen);
+		e = (unsigned char *) base64_encode(buf, len, &elen);
 	else
-		e = base64_decode(buf, len, &elen);
+		e = base64_decode((const char *) buf, len, &elen);
 	if (e == NULL)
 		return -2;
 	f = fopen(argv[3], "w");