NFC: st21nfcb: Avoid use of skb after free

Do not insert in send queue the skb that contains unknown Packet Control
Byte

Acked-by: Christophe Ricard <christophe-h.ricard@st.com>
Signed-off-by: Anda-Maria Nicolae <anda-maria.nicolae@intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>