Add ELF macros found in the aaelf64 spec

The arm64 aaelf64 spec [0] has DT_AARCH64_ that could be used with
dynamic linking. It also adds GNU_PROPERTY_AARCH64_FEATURE_1_AND used
to tell the kernel which CPU features the binary is compatible with,
but does not require to execute correctly.

Add these values so the kernel and elf tools can make use of them.

[0] https://github.com/ARM-software/abi-aa/blob/2021Q1/aaelf64/aaelf64.rst

Sponsored by: The FreeBSD Foundation