NFC: Add firmware upload netlink command

As several NFC chipsets can have their firmwares upgraded and
reflashed, this patchset adds a new netlink command to trigger
that the driver loads or flashes a new firmware. This will allows
userspace triggered firmware upgrade through netlink.
The firmware name or hint is passed as a parameter, and the driver
will eventually fetch the firmware binary through the request_firmware
API.
The cmd can only be executed when the nfc dev is not in use. Actual
firmware loading/flashing is an asynchronous operation. Result of the
operation shall send a new event up to user space through the nfc dev
multicast socket. During operation, the nfc dev is not openable and
thus not usable.

Signed-off-by: Eric Lapuyade <eric.lapuyade@intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>