drm/i915/dsc: drop redundant = 0 assignments

drm/i915/dsc: drop redundant = 0 assignments

Directly assign the values instead of first assigning 0 and then |= the
values.

Cc: Suraj Kandpal <suraj.kandpal@intel.com>
Cc: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/d752a148cc84558b76c8c3dacd9c0b2e0a4efd91.1693933849.git.jani.nikula@intel.com