mach-shmobile: Emma Mobile EV2 GPIO support V3

Tie in the Emma Mobile GPIO driver "em-gio" to
support the GPIOs on Emma Mobile EV2.

A static IRQ range is used to allow boards to
hook up their platform devices to the GPIOs.

DT support is still on the TODO for the GPIO driver,
so only platform device support is included here.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>