Input: ili210x - special case ili251x sample read out

The ili251x touch controller needs 5ms delay between sending I2C device
address and register address, and, writing or reading register data.

According to downstream ili251x example code, this 5ms delay is not
required when reading touch samples out of the controller. Implement
such a special case.
Signed-off-by: Marek Vasut <marex@denx.de>
Link: https://lore.kernel.org/r/20211108005259.480545-1-marex@denx.deSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/touchscreen/ili210x.c

@@ -224,15 +224,17 @@ static const struct ili2xxx_chip ili212x_chip = {
 	.has_calibrate_reg	= true,
 };
 
-static int ili251x_read_reg(struct i2c_client *client,
-			    u8 reg, void *buf, size_t len)
+static int ili251x_read_reg_common(struct i2c_client *client,
+				   u8 reg, void *buf, size_t len,
+				   unsigned int delay)
 {
 	int error;
 	int ret;
 
 	ret = i2c_master_send(client, &reg, 1);
 	if (ret == 1) {
-		usleep_range(5000, 5500);
+		if (delay)
+			usleep_range(delay, delay + 500);
 
 		ret = i2c_master_recv(client, buf, len);
 		if (ret == len)
@@ -244,12 +246,18 @@ static int ili251x_read_reg(struct i2c_client *client,
 	return ret;
 }
 
+static int ili251x_read_reg(struct i2c_client *client,
+			    u8 reg, void *buf, size_t len)
+{
+	return ili251x_read_reg_common(client, reg, buf, len, 5000);
+}
+
 static int ili251x_read_touch_data(struct i2c_client *client, u8 *data)
 {
 	int error;
 
-	error = ili251x_read_reg(client, REG_TOUCHDATA,
-				 data, ILI251X_DATA_SIZE1);
+	error = ili251x_read_reg_common(client, REG_TOUCHDATA,
+					data, ILI251X_DATA_SIZE1, 0);
 	if (!error && data[0] == 2) {
 		error = i2c_master_recv(client, data + ILI251X_DATA_SIZE1,
 					ILI251X_DATA_SIZE2);