drm/edid: use a better variable name for EDID block read retries

Just i is a bit terse, clarify what it's about.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/9c95c01445f5735332cbbd9eae6cd078e152050f.1648752228.git.jani.nikula@intel.com