drm/i915/display: change who adds [] around crtc state dump context string

Add the brackets [] around crtc state dump context string in
intel_crtc_state_dump() so the callers don't have to.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/c7d671279fb7d99eaf882bcb88c5c1d653755fb1.1655372759.git.jani.nikula@intel.com