nfc: st-nci: remove unnecessary label

in st_nci_spi_write function, first assign a value to a variable then
goto exit label. return statement just follow the label and exit label
just used once, so we should directly return and remove exit label.

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