Bluetooth: GATT: Fix not storing SC changes

CCC storaged is no longer declared separetly so check if ccc->cfg
matches with sc_ccc_cfg no longer works so instead use the cfg_changed
callback and match against sc_ccc_cfg_changed.

Fixes #19267

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>