drm/i915/tv: Fix TV mode

Commit 1fd4a5a3 ("drm/connector: Rename legacy TV property") failed
to update all the users of the struct drm_tv_connector_state mode field,
which resulted in a build failure in i915.

However, a subsequent commit in the same series reintroduced a mode
field in that structure, with a different semantic but the same type,
with the assumption that all previous users were updated.

Since that didn't happen, the i915 driver now compiles, but mixes
accesses to the legacy_mode field and the newer mode field, but with the
previous semantics.

This obviously doesn't work very well, so we need to update the accesses
that weren't in the legacy renaming commit.

Fixes: 1fd4a5a3

 ("drm/connector: Rename legacy TV property")
Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240220131251.453060-1-mripard@kernel.org