drm/i915/dsi: improve dphy param limits logging

Move the limit checks near the calculations for each field, and actually
log the values that exceed limits.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180419085940.21505-1-jani.nikula@intel.com