drm/edid: Fix minimum bpc supported with DSC1.2 for HDMI sink

HF-VSDB/SCDB has bits to advertise support for 16, 12 and 10 bpc.
If none of the bits are set, the minimum bpc supported with DSC is 8.

This patch corrects the min bpc supported to be 8, instead of 0.

Fixes: 76ee7b90 ("drm/edid: Parse DSC1.2 cap fields from HFVSDB block")
Cc: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Cc: Uma Shankar <uma.shankar@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

v2: s/DSC1.2/DSC 1.2

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220916100551.2531750-2-ankit.k.nautiyal@intel.com