cmd/compile: add Param to Sizeof test

Change-Id: I2a710f0e9b484b3dfc581d3a9a23aa13321ec267
Reviewed-on: https://go-review.googlesource.com/32316
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

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

@@ -24,6 +24,7 @@ func TestSizeof(t *testing.T) {
 	}{
 		{Func{}, 92, 160},
 		{Name{}, 44, 72},
+		{Param{}, 24, 48},
 		{Node{}, 92, 144},
 		{Sym{}, 60, 112},
 		{Type{}, 60, 96},