NFC: st21nfca: Add error messages for unexpected HCI events

Potentially an unexpected HCI event may occur because of a
firmware bug. It could be transparent for the user but we should
at least log it.

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