drm/msm: dsi: Initialize msm_dsi->id to -1

Currently msm_dsi->id is initialized to 0 during kzalloc. If bind fails
for a secondary dsi device before its id can be properly set (such as
during dt parsing), the id will point to the primary dsi device, causing
its reference to be removed from dsi_manager's global (msm_dsim_glb)
array.

This patch initializes the id to -1 and checks for negative in the
manager cleanup.

Cc: Doug Anderson <dianders@chromium.org>
Reviewed-by: Abhinav Kumar <abhinavk@codeaurora.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>

Signed-off-by: Rob Clark <robdclark@gmail.com>