target: msm8996: preserve programmable fetch configuration for HDMI interface

There are few usecase where the HDMI panel timings paramaters have low
vertical porches and programmable fetch needs to be enabled for such panels.

This changes preserves the programmable fetch bit configuration in the
interface config register.

Change-Id: I5253b1e9b9337ef87ede0a708163920fc9e0bcc0
Signed-off-by: Rahul Sharma <rahsha@codeaurora.org>