NFC: digital: Abort last command when dep link goes down

With this patch, the Digital Protocol layer abort the last issued
command when the dep link goes down. That way it does not have to wait
for the driver to reply with a timeout error before sending a new
command (i.e. a start poll command if constant polling is on).

Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>