Turns out the cursor is compatible with the pipe "HDR mode". It's
only the actual SDR planes that get entirely bypassed during
blending. So let's ignore the cursor when checking if we have
any planes active that aren't HDR compatible. This fixes the
regressions in the kms_cursor_crc and kms_plane_cursor tests.

Cc: Uma Shankar <uma.shankar@intel.com>
Cc: Shashank Sharma <shashank.sharma@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=110579
Fixes: 09b25812 ("drm/i915: Enable pipe HDR mode on ICL if only HDR planes are used")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190502200607.14504-2-ville.syrjala@linux.intel.comReviewed-by: Uma Shankar <uma.shankar@intel.com>