qcacmn: Clarify usage on Q_TARGET_ACCESS_BEGIN/END

Document where register writes are for legacy vs srng devices.
With the target access begin/end calls being associated with
the register writes and the register writes being associated to
specific HW, we avoid performing unneeded force wakes on common
code paths shared by legacy & srng based hardware.

Change-Id: Id91399d03298bfc5df56f0c5d5d14b648b665279
CRs-Fixed: 2117144
8 files changed