Fix the code style of macro in aarch64_neon_ad.m4

In JDK-8264352, the macro VECTOR_AND_NOT was added into aarch64_neon_ad.m4.
However, the align of `dnl` is wrong here. In this issue, I will fix it.
dnl $1 $2 $3 $4 $5
VECTOR_AND_NOT(2, I, D, 8, 8B)
VECTOR_AND_NOT(4, I, X, 16, 16B)
VECTOR_AND_NOT(2, L, X, 16, 16B)

I will fix other align problems in this issue.