Override AIDL CAS HAL if HIDL is built

android.hardware.cas@1.2-service gets built when API level is less than
or equal to 33, but com.android.hardware.cas gets built regardless,
this results in both getting built.

Test: m, observe CAS APEX not present for a device with a shipping API
      level of 30, inheriting base_vendor.mk.
Change-Id: I838cdaa31e38277a73bd22acb7b2490f076e779c