NFC: st21nfca: Remove useless err == 0 condition

On top of st21nfca_im_recv_atr_res_cb and st21nfca_im_recv_dep_res_cb a
condition if (err != 0) is present. Because err is never modified in the
code err will always be 0 at the end.

The condition can be removed.

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