The TRF7970A has configuration options to support hardware designs
which use a 27.12MHz clock. This commit adds a device tree option
'clock-frequency' to support configuring the this chip for default
13.56MHz clock or the optional 27.12MHz clock.
Acked-by: NRob Herring <robh@kernel.org>
Acked-by: NMark Greer <mgreer@animalcreek.com>
Signed-off-by: NGeoff Lansberry <geoff@kuvee.com>
Signed-off-by: NSamuel Ortiz <sameo@linux.intel.com>