gpio: Remove unused asm/gpio.h files

asm/gpio.h is included only by linux/gpio.h, and then only when the arch
selects ARCH_HAVE_CUSTOM_GPIO_H.  Only the following arches select it: arm
avr32 blackfin m68k (COLDFIRE only) sh unicore32.

Remove the unused asm/gpio.h files for the arches that do not select
ARCH_HAVE_CUSTOM_GPIO_H.

This is a follow-on to 7563bbf8 ("gpiolib/arches: Centralise
bolierplate asm/gpio.h").
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Acked-by: NThomas Gleixner <tglx@linutronix.de>
Acked-by: NArnd Bergmann <arnd@arndb.de>
Acked-by: NAlexandre Courbot <acourbot@nvidia.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>

arch/alpha/include/asm/gpio.h

-#ifndef __LINUX_GPIO_H
-#warning Include linux/gpio.h instead of asm/gpio.h
-#include <linux/gpio.h>
-#endif

arch/ia64/include/asm/gpio.h

-#ifndef __LINUX_GPIO_H
-#warning Include linux/gpio.h instead of asm/gpio.h
-#include <linux/gpio.h>
-#endif

arch/metag/include/asm/gpio.h

-#ifndef __LINUX_GPIO_H
-#warning Include linux/gpio.h instead of asm/gpio.h
-#include <linux/gpio.h>
-#endif

arch/microblaze/include/asm/gpio.h

-#ifndef __LINUX_GPIO_H
-#warning Include linux/gpio.h instead of asm/gpio.h
-#include <linux/gpio.h>
-#endif

arch/openrisc/include/asm/gpio.h

-#ifndef __LINUX_GPIO_H
-#warning Include linux/gpio.h instead of asm/gpio.h
-#include <linux/gpio.h>
-#endif

arch/powerpc/include/asm/gpio.h

-#ifndef __LINUX_GPIO_H
-#warning Include linux/gpio.h instead of asm/gpio.h
-#include <linux/gpio.h>
-#endif

arch/sparc/include/asm/gpio.h

-#ifndef __LINUX_GPIO_H
-#warning Include linux/gpio.h instead of asm/gpio.h
-#include <linux/gpio.h>
-#endif

arch/x86/include/asm/gpio.h

-#ifndef __LINUX_GPIO_H
-#warning Include linux/gpio.h instead of asm/gpio.h
-#include <linux/gpio.h>
-#endif

arch/xtensa/include/asm/gpio.h

-#ifndef __LINUX_GPIO_H
-#warning Include linux/gpio.h instead of asm/gpio.h
-#include <linux/gpio.h>
-#endif