ARM: pxa/spitz_pm: Fix hang when resuming from STR

Devices that use spitz_pm.c will fail to resume
from STR (Suspend To Ram) when the charger plug is inserted
or removed when a device is in STR mode. The culprit is
a misconfigured gpio line - GPIO18. GPIO18 should be configured as a
regular GPIO input but it gets configured as an alternate function
GPIO18_RDY. And then later in postsuspend() it gets configured as
a regular GPIO18 input line.

Fix this by removing the GPIO18_RDY configuration so that GPIO18
only gets configured as a regular gpio input.

Signed-off-by: Marko Katic <dromede@gmail.com>
Signed-off-by: Haojian Zhuang <haojian.zhuang@gmail.com>