[ARM] pxa/sharpsl_pm: cleanup of gpio-related code.

Replace calls to pxa_gpio_mode with respective gpio_request() /
gpio_direction_input(). In principle these calls can be dropped as
the only use of those GPIO are IRQs and IRQ code does setup GPIO
correctly.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Signed-off-by: Eric Miao <eric.miao@marvell.com>