kernel: gpio-button-hotplug: update to use threaded irq's

Many gpio controllers 'cansleep' due to the fact that they are behind busses
e.g. i2c etc.

Using threaded irq's allows for 'sleep-able' gpio's to be used.

Signed-off-by: Pushpal Sidhu <psidhu@gateworks.com>
Signed-off-by: Tim Harvey <tharvey@gateworks.com>

SVN-Revision: 48696