Remove unused LOCAL_ variables and related logic in...

Remove unused LOCAL_ variables and related logic in hardware/interfaces/compatibility_matrices/compatibility_matrix.mk.

After most compatibility_matrices Make modules have been moved to Android.bp there are some unused variables and logic, so remove them to reduce the complexity which helps conversion to Android.bp and reviewing.

Bug: 352234038
Test: CIs
Change-Id: Ic2f4538b3e50cc1ca573634cd46eb64c4013420a