drm/i915: Rename variables to be consistent with bspec

drm/i915: Rename variables to be consistent with bspec

Since the code seems insistent on using the variable names from the
bspec formulat, let's be consistent and use those names for all
the things. For some reason 'link_clk' and 'lanes' were left out
in the code until now.

Cc: Anshuman Gupta <anshuman.gupta@intel.com>
Cc: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200429185457.26235-2-ville.syrjala@linux.intel.com
Reviewed-by: Uma Shankar <uma.shankar@intel.com>