security/putty: fix ARM NEON AES-GCM code

Cherry-pick a test patch from upstream maintainer:

• this uses fallback code for compilers not providing vaddq_p128 (f.i. clang-10 on FreeBSD 12.3 AMD64/aarch64)
• and uses vaddq_p128 on systems that provide it, for instance, FreeBSD 13-STABLE AMD64/aarch64 with clang 14.0.5

Obtained from: Simon Tatham
MFH: 2022Q4

(cherry picked from commit 1632d93d92d9ba58401834a571ba89860963a171)