Input: cros_ec_keyb - remove redundant variable num_cols

Variable num_cols is being assigned but is never used hence it is
redundant and can be removed.

Cleans up clang warning:
warning: variable ‘num_cols’ set but not used [-Wunused-but-set-variable]
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/keyboard/cros_ec_keyb.c

@@ -160,9 +160,6 @@ static void cros_ec_keyb_process(struct cros_ec_keyb *ckdev,
 	int col, row;
 	int new_state;
 	int old_state;
-	int num_cols;
-
-	num_cols = len;
 
 	if (ckdev->ghost_filter && cros_ec_keyb_has_ghosting(ckdev, kb_state)) {
 		/*