deviceinfo: implement a new simple parser (MR 4)

This replaces an external toml library with a simple parser for
unmarshalling a deviceinfo.

main.go

@@ -29,14 +29,19 @@ func timeFunc(start time.Time, name string) {
 }
 
 func main() {
-	devinfo, err := deviceinfo.ReadDeviceinfo()
-	if err != nil {
+	deviceinfoFile := "/etc/deviceinfo"
+	if !exists(deviceinfoFile) {
 		log.Print("NOTE: deviceinfo (from device package) not installed yet, " +
 			"not building the initramfs now (it should get built later " +
 			"automatically.)")
 		return
 	}
 
+	devinfo, err := deviceinfo.ReadDeviceinfo(deviceinfoFile)
+	if err != nil {
+		log.Fatal(err)
+	}
+
 	outDir := flag.String("d", "/boot", "Directory to output initfs(-extra) and other boot files")
 	flag.Parse()