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-ppc4xx.c b/drivers/spi/spi-ppc4xx.c
index 7a85f22..af3e6e7 100644
--- a/drivers/spi/spi-ppc4xx.c
+++ b/drivers/spi/spi-ppc4xx.c
@@ -419,7 +419,7 @@
 	 * This includes both "null" gpio's and real ones.
 	 */
 	num_gpios = of_gpio_count(np);
-	if (num_gpios) {
+	if (num_gpios > 0) {
 		int i;
 
 		hw->gpios = kzalloc(sizeof(int) * num_gpios, GFP_KERNEL);
@@ -471,7 +471,7 @@
 		SPI_CPHA | SPI_CPOL | SPI_CS_HIGH | SPI_LSB_FIRST;
 
 	/* this many pins in all GPIO controllers */
-	bbp->master->num_chipselect = num_gpios;
+	bbp->master->num_chipselect = num_gpios > 0 ? num_gpios : 0;
 
 	/* Get the clock for the OPB */
 	opbnp = of_find_compatible_node(NULL, NULL, "ibm,opb");