NFC: nci: Move NFCEE discovery logic

NFCEE_DISCOVER_CMD is a specified NCI command used to discover
NFCEE IDs.
Move nci_nfcee_discover() call to nci_discover_se() in order to
guarantee:
- NFCEE_DISCOVER_CMD run when the NCI state machine is initialized
- NFCEE_DISCOVER_CMD is not run in case there is not discover_se
  hook defined by a NFC device driver.

Signed-off-by: Christophe Ricard <christophe-h.ricard@st.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>