drm/msm/sde: fix underrun interrupt enable index

Fix underrun enable index for command mode to
enable/disable it based on interface index instead
of pp index.

Change-Id: I119fa61ce68580bd4c2cc7c3c94d7353354bb348
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>
1 file changed