nfc: st-nci: remove unnecessary assignment and label

In function st_nci_hci_network_init, the variable r is assigned then
goto exit label, which just return r, so we use return to replace it.
and exit label only used once at here, so we remove exit label.

Signed-off-by: wengjianfeng <wengjianfeng@yulong.com>
Signed-off-by: David S. Miller <davem@davemloft.net>