drm/i915/tgl: Clamp min_cdclk to max_cdclk_freq to unblock 8K

We still need "Bump up CDCLK" workaround otherwise getting
underruns - however currently it blocks 8K as CDCLK = Pixel rate,
in 8K case would require CDCLK to be around 1 Ghz which is not
possible.

v2: - Convert to expression(max(min_cdclk, min(pixel_rate, max_cdclk))
      (Ville Syrjälä)
    - Use type specific min_t, max_t(Ville Syrjälä)

Fixes: 46d53e27 ("Revert "drm/i915: Remove unneeded hack now for CDCLK"")
Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200702091526.10096-1-stanislav.lisovskiy@intel.com