ARM: 7057/1: mach-pnx4008: rename GPIO header

The PNX4008 header file is using the generic gpio and gpiolib
namespace in <mach/gpio.h> yet the GPIO interface is not generic
at all so rename it to <mach/gpio-pnx4008.h>

This fixes a build failure in current -next: the includes were
changed from <mach/gpio.h> to <linux/gpio.h> but since this
platform isn't using generic gpio <linux/gpio.h> did not include
<mach/gpio.h> and things broke apart.

Acked-by: Vitaly Wool <vitalywool@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>