support wlan hotkey on Acer Travelmate 5735Z

On an Acer Travelmate 5735Z-452G32Mnss the WLAN-enable/disable key
doesn't send 0x1 as acpi event key code, but 0x3. This patch also
makes the module ignore hotkey acpi events for functions that are
already handled without. This avoids warning message "keyboard:
can't emulate rawmode for keycode 240".

Signed-off-by: Melchior FRANZ <mfranz@aon.at>
Signed-off-by: Matthew Garrett <mjg@redhat.com>