ARM: mmp: delete the custom GPIO header

The MMP sub-architecture appears to have a custom <mach/gpio.h>
for no reason whatsoever. The file became completely empty
after Haojian removed the remaining content in
commit 157d2644cb0c1e71a18baaffca56d2b1d0ebf10f
"ARM: pxa: change gpio to platform device".

Cc: Eric Miao <eric.y.miao@gmail.com>
Acked-by: Haojian Zhuang <haojian.zhuang@marvell.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

arch/arm/Kconfig

@@ -559,7 +559,6 @@ config ARCH_MMP
 	select GPIO_PXA
 	select IRQ_DOMAIN
 	select MULTI_IRQ_HANDLER
-	select NEED_MACH_GPIO_H
 	select PINCTRL
 	select PLAT_PXA
 	select SPARSE_IRQ

arch/arm/mach-mmp/include/mach/gpio.h

@@ -1,8 +0,0 @@
-#ifndef __ASM_MACH_GPIO_H
-#define __ASM_MACH_GPIO_H
-
-#include <asm-generic/gpio.h>
-
-#include <mach/cputype.h>
-
-#endif /* __ASM_MACH_GPIO_H */