drm/dp/i2c: send bare addresses to properly reset i2c connections (v4)

We need bare address packets at the start and end of
each i2c over aux transaction to properly reset the connection
between transactions.  This mirrors what the existing dp i2c
over aux algo currently does.

This fixes EDID fetches on certain monitors especially with
dp bridges.

v2: update as per Ville's comments
    - Set buffer to NULL for zero sized packets
    - abort the entre transaction if one of the messages fails
v3: drop leftover debugging code
v4: integrate Thierry's comments
    - add comments about address only transactions
    - switch back to i and j

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Thierry Reding <treding@nvidia.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Christian König <christian.koenig@amd.com>