qcacld-3.0: Remove block/unblock shutdown cb

Modem block/unblock shutdown callbacks are added to syncronize modem
shutdown when the driver is in deinit sequence.

With new changes everything is synchronized via the platform driver,
So remove the the block/unblock shutdown callback's.

Change-Id: If66eed5b51bbce64f024edf49e37a21b222a6a4c
CRs-Fixed: 2489733