fbdev: msm: Avoid adding videomode info twice

Calling mdss_fb_init_panel_modes results in adding the
videomode info twice to fb resulting in fb_match_mode
failure when mdss_fb_check_var is called.
To avoid this return early from panel_init_modes.

Change-Id: I3b38494ab71b287a2d839b8b8564bdc78de10279
Signed-off-by: Althaf Neelanchirayil <aneelanc@codeaurora.org>