drm/msm/dsi-staging: simulate esd trigger on display panel

Add capability to trigger an on demand esd from debugfs.
When esd is requested, it will pull reset gpio low causing
display panel to go into inactive state and next ESD status
check will attempt to do a full display recovery.

For example, the debugfs node for ESD trigger will be
available at /<debugfs-root>/<active display>/esd_trigger

Format for triggering an ESD:
"echo 1 > /d/dsi_nt35597_truly_dsc_cmd_display/esd_trigger"

CRs-Fixed: 2180708
Change-Id: I9550aa97ceb5c85d2566b285443a9323ac13fc75
Signed-off-by: Shashank Babu Chinta Venkata <sbchin@codeaurora.org>