drm/i915: Loop over all active pipes in intel_mbus_dbox_update

We need to loop through all active pipes, not just the ones, that
are in current state, because disabling and enabling even a particular
pipe affects credits in another one.

Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240402155016.13733-6-ville.syrjala@linux.intel.com