Fix warnings about unused variables

cli/x52_cli.c

@@ -333,7 +333,6 @@ static int do_help(const struct command_handler *cmd)
 int main(int argc, char **argv)
 {
     libx52_device *x52;
-    int command;
     struct string_map result;
     const struct command_handler *cmd;
     int i;

test/x52_test_mfd.c

@@ -78,8 +78,6 @@ int test_mfd_text(void)
 int test_mfd_display(void)
 {
     int i;
-    int j;
-    int rc;
     char str[16];
 
     print_banner("MFD display");