drm_mode_equal_no_clocks() is like drm_mode_equal() except it doesn't
compare the clock or vrefresh values. drm_mode_equal() is now
implemented by first doing the clock checks, and then calling
drm_mode_equal_no_clocks().

v2: Add missing EXPORT_SYMBOL()
Reviewed-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>