NFC: nci: Add firmware download support

A simple forward for firmware download (i.e. sending a new firmware
to the NFC adapter) from the NFC subsystem to the drivers.

This feature is required to update the firmware of NXP-NCI NFC
controllers but can be used by any NCI driver.

This feature has been present in the HCI subsystem since 9a695d.

Signed-off-by: Clément Perrochaud <clement.perrochaud@effinnov.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>