platform/x86: acer-wmi: Detect RF Button capability

If a machine reports a RF Button in the communication button device
bitmap, we need to remove it before calling Get Device Status otherwise
it will return the "Undefined device" (0xE2) error code.

Although this may be a BIOS bug, we don't really need to get or set the
RF Button status. The status indicator LED embedded in the button is
controlled by firmware logic, depending on the status of the wireless
radios present on the machine (WiFi || WWAN).

This commit fixes the wireless status indicator LED on the Acer
TravelMate P648-G2-MG, and cleans the following message from the kernel
log: "Get Current Device Status failed: 0xe2 - 0x0".

Signed-off-by: João Paulo Rechi Vita <jprvita@endlessm.com>
Reviewed-by: "Lee, Chun-Yi" <joeyli.kernel@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>