NFC: pn544: Add SE discover operation

For the SWP secure element, we send the proprietary SELF_TEST_SWP
command and check the response.
For the WI secure element, we simply try to switch to the default
embedded SE mode. If that works, it means we have an embedded SE.

Signed-off-by: Arron Wang <arron.wang@intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>