drm/msm/dsi-staging: handle panel init failure properly

Currently in driver even if panel init command transfer fails,
then driver is still setting panel init flag to true. This
causes subsequent failures and flooding of log when other panel
commands like backlight update, lp mode transition also fails
to transfer. Fix this by properly handling the panel init error.

Change-Id: I66d0e20aface67eb612420636ddfeb1f6a25cb86
Signed-off-by: Sandeep Panda <spanda@codeaurora.org>