drm/i915/tv: Use drm_mode_set_name() to name TV modes

No point in storing the mode names in the array. drm_mode_set_name()
will give us the same names without wasting space for these string
constants.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181112170000.27531-11-ville.syrjala@linux.intel.com


Reviewed-by: Imre Deak <imre.deak@intel.com>