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/sh/Kconfig b/arch/sh/Kconfig
index ff9e033..c40b29a 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -13,6 +13,7 @@
 	select HAVE_DMA_ATTRS
 	select HAVE_IRQ_WORK
 	select HAVE_PERF_EVENTS
+	select ARCH_HAVE_CUSTOM_GPIO_H
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG if (GUSA_RB || CPU_SH4A)
 	select PERF_USE_VMALLOC
 	select HAVE_KERNEL_GZIP