Fix STATUS_{NCI|HCI}_CMND in status register while processing command

This commit fixes the state of the status register during
command processing.

While the NFC device processes a command, no other command
might be submitted. Command processing is signalled to the
driver by setting STATUS_{NCI|HCI}_CMND in the status
register.

Signed-off-by: Thomas Zimmermann <tdz@users.sourceforge.net>