drm/amd/display: correct stream LTE_340MCSC_SCRAMBLE value

[Why]
HDMI 2.0 requires scrambling under specific conditions. We refer to
stream property LTE_340MCSC_SCRAMBLE to determine whether en/dis
scrambling.
While creating stream for sink, we setup LTE_340MCSC_SCRAMBLE by
referring to edid_caps. However, dm_helpers_parse_edid_caps()
doesn't construct HDMI Forum block data for edid_caps.
Moreover, fill_stream_properties_from_drm_display_mode() aslo
unconsciously clear the LTE_340MCSC_SCRAMBLE flag.

[How]
Drm already provides drm_display_info to refer HDMI Forum vsdb info.
Set stream LTE_340MCSC_SCRAMBLE by drm_display_info and remove
memset in fill_stream_properties_from_drm_display_mode()

Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
Reviewed-by: Nicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>