cmd/compile: clean up C-style variable declarations in plive.go

Change-Id: I928f51a1fe4830a81d4f5d3eb572785e06a75b77
Reviewed-on: https://go-review.googlesource.com/20581Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/compile/internal/gc/bv.go

@@ -105,7 +105,7 @@ func bvget(bv Bvec, i int32) int {
 
 // bvnext returns the smallest index >= i for which bvget(bv, i) == 1.
 // If there is no such index, bvnext returns -1.
-func bvnext(bv Bvec, i int32) int {
+func bvnext(bv Bvec, i int32) int32 {
 	if i >= bv.n {
 		return -1
 	}
@@ -131,7 +131,7 @@ func bvnext(bv Bvec, i int32) int {
 		i++
 	}
 
-	return int(i)
+	return i
 }
 
 func bvisempty(bv Bvec) bool {