NFC: st21nfcb: Remove inappropriate kfree on a devm_kzalloc pointer

Since ndev->driver_data is allocated by devm_kzalloc(), we do not
need the inappropriate kfree to free it in driver's remove function.
Freeing will trigger when driver unloads.

Cc: stable@vger.kernel.org
Acked-by: Christophe Ricard <christophe-h.ricard@st.com>
Signed-off-by: Firo Yang <firogm@gmail.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>