NFC: nci: remove current SLEEP mode management

NCI deactivate management was modified to support all NCI
deactivation type. Problem is that all the API are not ready
yet for it.

Problem is that with current code, when neard asks to deactivate
the tag it sends a deactivate SLEEP but nobody will then send a
IDLE deactivate. This IDLE deactivate is mandatory since NFC
controller can only be unlocked by DH.

Signed-off-by: Vincent Cuissard <cuissard@marvell.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>