slim: slim-msm: Synchronize xfer operation and ISR

Trigger complete signal after finishing the whole
operation in interrupt so that transfer function which
is waiting for the interrupt will go ahead in turn off
the clocks.

Change-Id: I3409929039a7de7da6379810a8b95dc15529058e
Signed-off-by: Dilip Kota <dkota@codeaurora.org>