Add a driver for the Texas Instruments TRF7970a RFID/NFC/15693
transceiver. The driver currently supports ISO/IEC 14443 Type 2
tags only (MIFARE Ultralight and Ultralight C but not Classic).
CC: Erick Macias <emacias@ti.com> CC: Felipe Balbi <balbi@ti.com> Signed-off-by: Mark A. Greer <mgreer@animalcreek.com> Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>