nfc: st21nfca: Add additional comments about EVT_TRANSACTION

Add comments about HCI EVT_TRANSACTION in order to make the code
understandable by other readers.

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