cmd/compile: leave the horses alone

I don't know why we were eliminating horses, this not cool.

Change-Id: I0d4b5a1b2f584e071de0a85ef88f9baf9183e12e
Reviewed-on: https://go-review.googlesource.com/c/go/+/712820
Reviewed-by: David Chase <drchase@google.com>
Auto-Submit: Jorropo <jorropo.pgm@gmail.com>
Reviewed-by: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>

Author: Jorropo

src/cmd/compile/internal/ssa/compile.go

@@ -585,7 +585,7 @@ var passOrder = [...]constraint{
 	{"memcombine", "lower"},
 	// late opt transform some CondSelects into math.
 	{"branchelim", "late opt"},
-	// ranchelim is an arch-independent pass.
+	// branchelim is an arch-independent pass.
 	{"branchelim", "lower"},
 }