Input: zforce - reduce stack memory allocated to frames

A frame is a u8 array with the following structure:
[PAYLOAD_HEADER, PAYLOAD_LENGTH, ...PAYLOAD_BODY...]

PAYLOAD_BODY can be at most 255 bytes long, as it's size is represented
by PAYLOAD_LENGTH. Therefore we can reduce the stack memory allocated to
payload_buffer[] roughly by half, from 512 to 257 bytes.
Signed-off-by: Luis Ortega <luiorpe1@upv.es>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Heiko Stuebner <heiko@sntech.de> - bq Cervantes (imx6sl)
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/touchscreen/zforce_ts.c

@@ -33,6 +33,7 @@
 #define WAIT_TIMEOUT		msecs_to_jiffies(1000)
 
 #define FRAME_START		0xee
+#define FRAME_MAXSIZE		257
 
 /* Offsets of the different parts of the payload the controller sends */
 #define PAYLOAD_HEADER		0
@@ -464,7 +465,7 @@ static irqreturn_t zforce_interrupt(int irq, void *dev_id)
 	struct i2c_client *client = ts->client;
 	const struct zforce_ts_platdata *pdata = dev_get_platdata(&client->dev);
 	int ret;
-	u8 payload_buffer[512];
+	u8 payload_buffer[FRAME_MAXSIZE];
 	u8 *payload;
 
 	/*