msm_serial_hs: Manage wake unlock delay

Current implementation of wake locks wait for
around 500msec while releasing the wakelock. This
prevents the system suspend for that much time after
the rx operation is done to ensure that all the data
delivered to the client before system suspend.
But some clients may take care of this in their
implementation. In this case uart driver no need to
wait before releasing the wakelock.
Hence, given the control to the client as a dtsi entry
to take decision on waiting before releasing the wakelock.

Change-Id: Ie32a0b76899963e7700ba378906fa4f9b3fa3ba4
Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>
Signed-off-by: Dilip Kota <c_dkota@codeaurora.org>