Fix Beam&Tag failures after opening NFC-EE.

An earlier MR1 checkin stopped re-registering the remote
device notification callback with libnfc on start_discovery.
This causes a regression since opening the NFC-EE will change
the callback. So Tag&Beam notifications end up going to
the secure element callback - causing crashes or missed tags.

Bug: 5725521
Change-Id: Idddba26b7babae095c124fda44e5b1da37549acd