kernel: spi: allow setting chipselect gpio to sleep

Fixes issues on some ar71xx MikroTik RouterBoard devices

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

target/linux/generic/patches-4.4/106-spi-use-gpio_set_value_cansleep-for-setting-chipsele.patch

@@ -0,0 +1,21 @@
+From: Felix Fietkau <nbd@nbd.name>
+Date: Fri, 30 Dec 2016 14:53:45 +0100
+Subject: [PATCH] spi: use gpio_set_value_cansleep for setting chipselect GPIO
+
+Sleeping is safe inside spi_transfer_one_message, and some GPIO chips
+need to sleep for setting values
+
+Signed-off-by: Felix Fietkau <nbd@nbd.name>
+---
+
+--- a/drivers/spi/spi.c
++++ b/drivers/spi/spi.c
+@@ -674,7 +674,7 @@ static void spi_set_cs(struct spi_device
+ 		enable = !enable;
+ 
+ 	if (gpio_is_valid(spi->cs_gpio))
+-		gpio_set_value(spi->cs_gpio, !enable);
++		gpio_set_value_cansleep(spi->cs_gpio, !enable);
+ 	else if (spi->master->set_cs)
+ 		spi->master->set_cs(spi, !enable);
+ }