[sanitizer] Use same shadow offset for ASAN on aarch64

This patch makes ASAN for aarch64 use the same shadow offset for all
currently supported VMAs (39 and 42 bits).  The shadow offset is the
same for 39-bit (36).  Similar to ppc64 port, aarch64 transformation
also requires to use an add instead of 'or' for 42-bit VMA.

llvm-svn: 252495