cmd/compile: remove 8-byte alignment requirement of stack slot on s390x
cmd/compile: remove 8-byte alignment requirement of stack slot on s390x

This CL applies CL 267999 to s390x.

Updates #42385

Change-Id: Ie8e69ad1b3f7ddc2c8f05125f4af617aeac035ec
Reviewed-on: https://go-review.googlesource.com/c/go/+/297769
Reviewed-by: Keith Randall <8c99c3a9284e493be632950b84cd789d08ed3e9d@golang.org>
Trust: eric fang <68c7b5ebe4a86ef7e52157f5950041656bf82310@arm.com>

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