drm: msm: Cleanup drm_display_mode print str

This patch adjust the print string of drm_display_mode object
to remove drm_mode_object dependency in msm files.

Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Shayenne Moura <shayenneluzmoura@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/3e2dcd38c964061f245b0ae22186c71da06e9742.1547143069.git.shayenneluzmoura@gmail.com