ACPI: bus: Indicate support for the Generic Event Device thru _OSC

A device driver for the Generic Event Device (ACPI0013) already
exists for quite some time, but support for it was never reported
thru _OSC.

Fix this by setting bit 11 ("Generic Event Device support") when
evaluating _OSC.

Fixes: 3db80c23 ("ACPI: implement Generic Event Device")
Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>