This is part of the work making gpio.c generic enough, the changes
include:
1. move IRQ handling of GPIO 0 and 1 outside (and back into irq.c)
2. pxa_init_gpio() accepts a range for muxed GPIO IRQs, and an IRQ
number for the muxed GPIOs
3. __gpio_is_occupied() and __gpio_is_inverted() are made inline,
and are moved into <mach/gpio.h> instead of generic gpio.c
Signed-off-by: Eric Miao <eric.miao@marvell.com>