cmd/compile: fix loong64 MINF → FMINF name and friends

cmd/compile: fix loong64 MINF → FMINF name and friends

CL 580283 left cmd/compile/internal/ssa/_gen/ in a state where `go run *.go` would always fails ! :'(

Change-Id: I0b3aea9b3f6275cb17c552898c5034e15f0107d5
Reviewed-on: https://go-review.googlesource.com/c/go/+/603995
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: David Chase <drchase@google.com>