1. add common GPIO handling code into [arch/arm/plat-pxa]
2. common code in <mach/gpio.h> moved into <plat/gpio.h>, new processors
should implement its own <mach/gpio.h>, provide the following required
definitions and '#include <plat/gpio.h>' in the end:
- GPIO_REGS_VIRT for mapped virtual address of the GPIO registers'
physical I/O memory
- macros of GPLR(), GPSR(), GPDR() for constant optimization for
functions gpio_{set,get}_value() (so that bit-bang code can still
have tolerable performance)
- NR_BUILTIN_GPIO for the number of onchip GPIO
- definitions of __gpio_is_inverted() and __gpio_is_occupied(), they
can be either macros or inlined functions
Signed-off-by: Eric Miao <eric.miao@marvell.com>