drm/msm/sde: fix programmable fetch config start

For sdm855 the display interface was redesigned due to the FIFO
removal in the DSI controller. As a result the DSI controller data
consumption has been decoupled from the timing control.
The data throttling can extend into the next line pushing out the
earliest time programmable fetch can begin. This change effectively
adds another line to the fetch config start position.

Change-Id: I7159d5131d69dd0ef0a424cb03a88f06f14ee3de
Signed-off-by: Abhijit Kulkarni <kabhijit@codeaurora.org>