cmd/5g etc: tweak import blocks

Remove blank lines and merge lone imports into blocks.

Change-Id: Ib46dad584456909969f1ba3a2c7f5667abf336ae
Reviewed-on: https://go-review.googlesource.com/6792
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
diff --git a/src/cmd/9g/ggen.go b/src/cmd/9g/ggen.go
index d9bcfb7..3cca4a5 100644
--- a/src/cmd/9g/ggen.go
+++ b/src/cmd/9g/ggen.go
@@ -5,11 +5,11 @@
 package main
 
 import (
+	"cmd/internal/gc"
 	"cmd/internal/obj"
 	"cmd/internal/obj/ppc64"
 	"fmt"
 )
-import "cmd/internal/gc"
 
 func defframe(ptxt *obj.Prog) {
 	var n *gc.Node