input: touchscreen: atmel_mxt_ts: fix smatch warnings

Fixes smatch warnings for :
drivers/input/touchscreen/atmel_mxt_ts.c:427 mxt_debug_msg_enable() warn: inconsistent returns 'mutex:&data->debug_msg_lock'.
   Locked on:   line 422
   Unlocked on: line 415
drivers/input/touchscreen/atmel_mxt_ts.c:471 mxt_debug_msg_add() warn: inconsistent returns 'mutex:&data->debug_msg_lock'.
   Locked on:   line 455
   Unlocked on: line 471
drivers/input/touchscreen/atmel_mxt_ts.c:1496 mxt_interrupt() error: we previously assumed 'data->flash' could be null (see line 1493)

Fixes "5a23661" (atmel_mxt_ts.c: move to current github.com/atmel-maxtouch)
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>

Author: ehristev

drivers/input/touchscreen/atmel_mxt_ts.c

@@ -418,8 +418,10 @@ static void mxt_debug_msg_enable(struct mxt_data *data)
 
 	data->debug_msg_data = kcalloc(DEBUG_MSG_MAX,
 				data->T5_msg_size, GFP_KERNEL);
-	if (!data->debug_msg_data)
+	if (!data->debug_msg_data) {
+		mutex_unlock(&data->debug_msg_lock);
 		return;
+	}
 
 	data->debug_v2_enabled = true;
 	mutex_unlock(&data->debug_msg_lock);
@@ -451,6 +453,7 @@ static void mxt_debug_msg_add(struct mxt_data *data, u8 *msg)
 	mutex_lock(&data->debug_msg_lock);
 
 	if (!data->debug_msg_data) {
+		mutex_unlock(&data->debug_msg_lock);
 		dev_err(dev, "No buffer!\n");
 		return;
 	}
@@ -685,6 +688,9 @@ static int mxt_check_bootloader(struct mxt_data *data)
 	u8 state;
 	int ret;
 
+	if (!f)
+		return -EINVAL;
+
 	/* Handle interrupt after download/flash process */
 	if (f->pos >= f->fw->size) {
 		complete(&f->flash_completion);