We're currently failing to reset everything in display_info.hdmi
which will potentially cause us to use stale information when
swapping monitors. Eg. if the user replaces a HDMI 2.0 monitor
with a HDMI 1.x monitor we will continue to think that the monitor
supports scrambling. That will lead to a black screen since the
HDMI 1.x monitor won't understand the scrambled signal.

Fix the problem by clearing display_info.hdmi fully. And while at
eliminate some duplicated code by calling drm_reset_display_info()
in drm_add_display_info().

Cc: stable@vger.kernel.org
Cc: Antony Chen <antonychen@qnap.com>
Cc: Shashank Sharma <shashank.sharma@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105655Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180424130250.7028-1-ville.syrjala@linux.intel.comReviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Tested-by: Antony Chen <antonychen@qnap.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>