drm/i915/dsc: Fix bigjoiner check in dsc_disable

drm/i915/dsc: Fix bigjoiner check in dsc_disable

This change takes care of resetting the dss_ctl registers
in case of dsc_disable, bigjoiner disable and also
uncompressed joiner disable.

v2: Fix formatting
v3: Fix the typo (Mansi)

Suggested-by: Jani Nikula <jani.nikula@intel.com>
Fixes: d961eb20adb6 ("drm/i915/bigjoiner: atomic commit changes for uncompressed joiner")
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/3537
Signed-off-by: Vandita Kulkarni <vandita.kulkarni@intel.com>
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210609065914.4454-1-vandita.kulkarni@intel.com