arm64: HWCAP/HWCAP2 aux args support for 32-bit ARM binaries.

This fixes build/run of golang under COMPAT32 emulation.

PR: 256897
Reviewed by: andrew, mmel, manu, jhb, cognet, Robert Clausecker
Tested by: brd, andrew, Robert Clausecker
MFC after: 3 weeks
Relnotes: yes
Sponsored by: Rubicon Communications, LLC ("Netgate")
Differential Revision: https://reviews.freebsd.org/D31175