acer-wmi: support Lenovo ideapad S205 wifi switch

The AMW0 function in acer-wmi works on Lenovo ideapad S205 for control
the wifi hardware state. We also found there have a 0x78 EC register
exposes the state of wifi hardware switch on the machine.

So, add this patch to support Lenovo ideapad S205 wifi hardware switch
in acer-wmi driver.

Reference: bko#37892
	https://bugzilla.kernel.org/show_bug.cgi?id=37892



Cc: Carlos Corbacho <carlos@strangeworlds.co.uk>
Cc: Matthew Garrett <mjg@redhat.com>
Cc: Dmitry Torokhov <dtor@mail.ru>
Cc: Corentin Chary <corentincj@iksaif.net>
Cc: Thomas Renninger <trenn@suse.de>
Tested-by: Florian Heyer <heyho@flanto.de>
Signed-off-by: Lee, Chun-Yi <jlee@suse.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>