msm: mdss: disable dsi burst mode when idle is enabled

When driver programs dsi to add an idle delay,
burst mode needs to be disabled so the
idle delay is inserted between packets.
This change makes sure that burst mode gets
disabled when idle is enabled, fixing some
corruption shown in jdi panel that needs an
extra delay during partial update for small
widths.

CRs-Fixed: 959818
Change-Id: Ida840302f9f5313e46e3d27933c40bfc2b65e8f7
Signed-off-by: Ingrid Gallardo <ingridg@codeaurora.org>