ARM: dts: omap4-devkit8000: fix gpmc ranges property

With two separate &gpmc nodes the second ranges property overwrites the
first. So put nand and ethernet in a single node and merge the ranges.

While at it also fix the ethernet suffix.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Tony Lindgren <tony@atomide.com>