cmd/compile/internal/ir: remove OFUNCINST and InstExpr
These were only ever used by the pre-unified generics frontend. I
initially kept them because I thought they'd be useful for the unified
frontend eventually too, but that hasn't manifested.
Change-Id: Iaa31a76ac4d62533ec269d2a7141442b8e344180
Reviewed-on: https://go-review.googlesource.com/c/go/+/520608
Auto-Submit: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>