drm/i915: Allow fuzzy matching in pipe_config_compare, v2.

Instead of doing ad-hoc checks we already have a way of checking
if the state is compatible or not. Use this to force a modeset.

Only during modesets, or with PIPE_CONFIG_QUIRK_INHERITED_MODE
we should check if a full modeset is really needed.

Fastboot will allow the adjust parameter to ignore some stuff
too, and it will fix up differences in state that are ignored
by the compare function.

Changes since v1:
- Increase the value of the lowest m/n to prevent truncation.
- Dump pipe config when fastboot's used, without a modeset.
- Add adjust parameter to intel_compare_link_m_n, which is
  used to adjust m2_n2 if it's a multiple of m_n.
- Add exact parameter intel_compare_m_n.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>