cmd/compile: remove racefuncenterfp when it is not needed

We already remove racefuncenter and racefuncexit if they are not
needed (i.e. the function doesn't have any other race  calls).
racefuncenterfp is like racefuncenter but used on LR machines.
Remove unnecessary racefuncenterfp as well.

Change-Id: I65edb00e19c6d9ab55a204cbbb93e9fb710559f1
Reviewed-on: https://go-review.googlesource.com/c/go/+/267099


Trust: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>