ar71xx: fix regression in 74x164 initialization with 4.9

The memcpy of the init data relies on chip->registers to be initialized,
which only happens later in the code. Move this initialization further
down to make it work.
This was breaking PCIe/USB on some MikroTik RouterBoard devices.

Signed-off-by: Felix Fietkau <nbd@nbd.name>

target/linux/ar71xx/patches-4.9/451-gpio-74x164-improve-platform-device-support.patch

@@ -25,7 +25,7 @@
  	/*
  	 * bits_per_word cannot be configured in platform data
  	 */
-@@ -115,17 +123,23 @@ static int gen_74x164_probe(struct spi_d
+@@ -115,12 +123,15 @@ static int gen_74x164_probe(struct spi_d
  	if (ret < 0)
  		return ret;
  
@@ -47,15 +47,7 @@
  
  	chip = devm_kzalloc(&spi->dev, sizeof(*chip) + nregs, GFP_KERNEL);
  	if (!chip)
- 		return -ENOMEM;
- 
-+	if (pdata && pdata->init_data)
-+		memcpy(chip->buffer, pdata->init_data, chip->registers);
-+	
- 	spi_set_drvdata(spi, chip);
- 
- 	chip->gpio_chip.label = spi->modalias;
-@@ -133,7 +147,11 @@ static int gen_74x164_probe(struct spi_d
+@@ -133,7 +144,11 @@ static int gen_74x164_probe(struct spi_d
  	chip->gpio_chip.get = gen_74x164_get_value;
  	chip->gpio_chip.set = gen_74x164_set_value;
  	chip->gpio_chip.set_multiple = gen_74x164_set_multiple;
@@ -68,6 +60,16 @@
  
  	chip->registers = nregs;
  	chip->gpio_chip.ngpio = GEN_74X164_NUMBER_GPIOS * chip->registers;
+@@ -142,6 +157,9 @@ static int gen_74x164_probe(struct spi_d
+ 	chip->gpio_chip.parent = &spi->dev;
+ 	chip->gpio_chip.owner = THIS_MODULE;
+ 
++	if (pdata && pdata->init_data)
++		memcpy(chip->buffer, pdata->init_data, chip->registers);
++
+ 	mutex_init(&chip->lock);
+ 
+ 	ret = __gen_74x164_write_config(chip);
 @@ -170,17 +188,19 @@ static int gen_74x164_remove(struct spi_
  	return 0;
  }