drm/msm/dsi-staging: fix multiple reg read in ESD

In the current implementation when ESD check needs
to send multiple read commands then the last command
flag is only set for first read command. So the
transfer of rest of the read commands will fail. This
changes fixes all the issues related to multiple
reg read feature.

Change-Id: If783c9e7bc15630358d2cb1f6cd5a6b3320fbf6d
Signed-off-by: Sandeep Panda <spanda@codeaurora.org>