powerpc: 85xx rdb: move np pointer to avoid builderror

If CONFIG_UCC_GETH or CONFIG_SERIAL_QE is not defined then we get a
warning about an used variable which leads to a build error.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Scott Wood <scottwood@freescale.com>