disp: msm: sde: fix ich reset override logic

This change fixes the detection logic for overriding the ich
reset in both single and dual dsc case. In the previous logic
ich reset override was not getting triggered when partial update
on single dsc was enabled. This override is required to change the
default Hw behavior of changing the ich reset position.

ICH reset needs to be overridden in dual dsc merge case when
partial update disables the dsc merge and no. of slices per
encoder drops to 1. Similarly for single dsc case partial update
case when DSC encoder configuration changes from 2 slices to
single slice this override is required.

Change-Id: I435dc7ff10c9fb0edb8e40e6701608aa22136981
Signed-off-by: Abhijit Kulkarni <kabhijit@codeaurora.org>