nfc: st-nci: Add spi phy support for st21nfcb

st21nfcb does support another phy than i2c: spi.
st21nfcc does not support spi as the spi ios are used
by the AMS RF booster.

st21nfcb is not following NCI NFC Forum recommendations for spi
but rely on ST prioritary protocol ndlc as for i2c.

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