It is intended to replace pn533_send_cmd_frame_sync() iface which
requires from the caller to create complete frame.

The new function constructs a complete frame itself and sends it out
in sync manner. This way frame logic is hidden from the caller.

pn533_send_cmd_sync() returns ERR_PTR in case of an error or a pointer
to valid response sk_buff otherwise. The pointer must be freed by the
caller when it's been consumed.
Signed-off-by: Waldemar Rymarkiewicz <waldemar.rymarkiewicz@tieto.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>