DO NOT MERGE: Fix incorrect TARGET_2ND_CPU_VARIANT for A/B devices

TARGET_2ND_CPU_VARIANT for non A/B devices has been changed to
cortex-a15 for better performance. Do the same for A/B devices.

Bug: 65042524
Test: build with aosp_arm64_ab
Change-Id: Id67c2779d2170f29b278c1c8a9ac513aa76a620d
1 file changed