bta_gattc: Fix number of max gatt connection client control blocks

Each GATT client application in worst case might have instance per
connection.
Without this change and having LeAudio support which per set of CSIP
based devices might take up to 12 GATT clients (vc, leaudio, csip,
battery service, bass, hap) * 2, the pool will end very quickly

Bug: 325438660
Test: mmm packages/modules/Bluetooth
Flag: Exempt, just increase number of control blocks for avoid future
issues
Test: manual testing multiple devices connection

Change-Id: Ia359091ae9026ac5a8e5980d883e0fbe20001e18