cmd/compile: remove 8-byte alignment requirement of stack slot on ppc64
cmd/compile: remove 8-byte alignment requirement of stack slot on ppc64

This CL applies CL 267999 to ppc64.

Fixes #42385

Change-Id: I6462d647d1abdf7cec99607c40ef4d1fed1941e5
Reviewed-on: https://go-review.googlesource.com/c/go/+/297770
Reviewed-by: eric fang <68c7b5ebe4a86ef7e52157f5950041656bf82310@arm.com>
Reviewed-by: Cherry Zhang <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>
Trust: eric fang <68c7b5ebe4a86ef7e52157f5950041656bf82310@arm.com>

golang/go,golang/go,cloudflare/go,CAFxX/go,cloudflare/go,golang/go,CAFxX/go,CAFxX/go,golang/go,CAFxX/go,cloudflare/go,cloudflare/go,nawawi/go,nawawi/go,nawawi/go,CAFxX/go,cloudflare/go,golang/go,golang/go,golang/go,CAFxX/go,CAFxX/go,nawawi/go,cloudflare/go,CAFxX/go,cloudflare/go,nawawi/go,nawawi/go,golang/go,nawawi/go,nawawi/go,cloudflare/go