drm/dsc: fix drm_edp_dsc_sink_output_bpp() DPCD high byte usage

drm/dsc: fix drm_edp_dsc_sink_output_bpp() DPCD high byte usage

The operator precedence between << and & is wrong, leading to the high
byte being completely ignored. For example, with the 6.4 format, 32
becomes 0 and 24 becomes 8. Fix it, and remove the slightly confusing
and unnecessary DP_DSC_MAX_BITS_PER_PIXEL_HI_SHIFT macro while at it.

Fixes: 0575650077ea ("drm/dp: DRM DP helper/macros to get DP sink DSC parameters")
Cc: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Cc: Manasi Navare <navaremanasi@google.com>
Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
Cc: <stable@vger.kernel.org> # v5.0+
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230406134615.1422509-1-jani.nikula@intel.com