gpio: allow setting ARCH_NR_GPIOS from Kconfig

The ARM version of asm/gpio.h basically just contains the same definitions
as the gpiolib version, with the exception of ARCH_NR_GPIOS.

This adds the option for overriding the constant through Kconfig to
the architecture-independent header, so we can remove the ARM specific
file later.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

include/asm-generic/gpio.h

@@ -26,8 +26,12 @@
  */
 
 #ifndef ARCH_NR_GPIOS
+#if defined(CONFIG_ARCH_NR_GPIO) && CONFIG_ARCH_NR_GPIO > 0
+#define ARCH_NR_GPIOS CONFIG_ARCH_NR_GPIO
+#else
 #define ARCH_NR_GPIOS		512
 #endif
+#endif
 
 /*
  * "valid" GPIO numbers are nonnegative and may be passed to