drm/i915/display: Drop dead code from hsw_read_infoframe()

HSW_TVIDEO_DIP_CTL is read but not used.

Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210418002126.87882-4-jose.souza@intel.com