NFC: Extend and fix the internal secure element API

Secure elements need to be discovered after enabling the NFC controller.
This is typically done by the NCI core and the HCI drivers (HCI does not
specify how to discover SEs, it is left to the specific drivers).
Also, the SE enable/disable API explicitely takes a SE index as its
argument.

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>