gpio: Make of_count_named_gpios() use new of_count_phandle_with_args()

This patch replaces the horribly coded of_count_named_gpios() with a
call to of_count_phandle_with_args() which is far more efficient. This
also changes the return value of of_gpio_count() & of_gpio_named_count()
from 'unsigned int' to 'int' so that it can return an error code. All
the users of that function are fixed up to correctly handle a negative
return value.

v2: Split GPIO portion into a separate patch

Tested-by: Andreas Larsson <andreas@gaisler.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Rob Herring <rob.herring@calxeda.com>
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 19ee901..21c4748 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1059,15 +1059,14 @@
 #ifdef CONFIG_OF
 static int of_spi_register_master(struct spi_master *master)
 {
-	u16 nb;
-	int i, *cs;
+	int nb, i, *cs;
 	struct device_node *np = master->dev.of_node;
 
 	if (!np)
 		return 0;
 
 	nb = of_gpio_named_count(np, "cs-gpios");
-	master->num_chipselect = max(nb, master->num_chipselect);
+	master->num_chipselect = max(nb, (int)master->num_chipselect);
 
 	if (nb < 1)
 		return 0;