drm/i915: Drop the redundant hdmi prefix/suffix from a lot of variables

drm/i915: Drop the redundant hdmi prefix/suffix from a lot of variables

A bunch of functions are now exclusively used for HDMI, so naming the
variables with hdmi prefix/suffix is redundant. Also use int rather
than u32 for the translation level consistently.

v2: Rebase due to hdmi_level=-1 avoidance

Cc: James Ausmus <james.ausmus@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171018181958.4423-1-ville.syrjala@linux.intel.com
Reviewed-by: James Ausmus <james.ausmus@intel.com>