[arch][arm64] Parse BRK exception
[arch][arm64] Parse BRK exception

When a crash is because of a BRK instruction, print that instead of
the default "unhandled synchronous exception".

Bug: 179516283


Change-Id: I9667d7157d24a79e2b2ceb7ef283ebc2b09398d0

littlekernel/lk,hollanderic/lkstuff,littlekernel/lk,hollanderic/lkstuff,littlekernel/lk,hollanderic/lkstuff,littlekernel/lk,hollanderic/lkstuff