gpiolib/arches: Centralise bolierplate asm/gpio.h

Rather than requiring architectures that use gpiolib but don't have any
need to define anything custom to copy an asm/gpio.h provide a Kconfig
symbol which architectures must select in order to include gpio.h and
for other architectures just provide the trivial implementation directly.

This makes it much easier to do gpiolib updates and is also a step towards
making gpiolib APIs available on every architecture.

For architectures with existing boilerplate code leave a stub header in
place which warns on direct inclusion of asm/gpio.h and includes
linux/gpio.h to catch code that's doing this.  Direct inclusion of
asm/gpio.h has long been deprecated.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Jonas Bonn <jonas@southpole.se>
Acked-by: Tony Luck <tony.luck@intel.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
diff --git a/arch/blackfin/Kconfig b/arch/blackfin/Kconfig
index 373a690..bf3d80f 100644
--- a/arch/blackfin/Kconfig
+++ b/arch/blackfin/Kconfig
@@ -31,6 +31,7 @@
 	select HAVE_KERNEL_LZO if RAMKERNEL
 	select HAVE_OPROFILE
 	select HAVE_PERF_EVENTS
+	select ARCH_HAVE_CUSTOM_GPIO_H
 	select ARCH_WANT_OPTIONAL_GPIOLIB
 	select HAVE_GENERIC_HARDIRQS
 	select GENERIC_ATOMIC64