cmd/compile: mark generated eq/hash functions as //go:noinline

cmd/compile: mark generated eq/hash functions as //go:noinline

Instead of having the inliner specially recognize that eq/hash
functions can't be inlined, change the geneq and genhash to mark them
as //go:noinline.

This is a prereq for a subsequent CL that will move more logic for
handling rtypes from package types to package reflectdata.

Change-Id: I091a9ededcc083fe8305cf5443a9af7d3a9053b6
Reviewed-on: https://go-review.googlesource.com/c/go/+/518955
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Auto-Submit: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>