NFC: Introduce vendor commands structures

Together with inline routines to associate a vendor commands
array with an NFC device.

Vendor commands allow vendors to implement their very specific
operations from driver code instead of adding new stack ops
for non NFC generic commands.
Vendors need to select their own unique IDs and use that as a
namespace for defining sub commands.

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