ARM: dts: Update Nanobone dts file to add external FRAM chip

From v4.2+ the GPMC code has been changed to reset all the bootloader
GPMC settings when the kernel starts.

As such, this DTS file now needs the external FRAM defined.

Signed-off-by: Mark Jackson <mpfj@newflow.co.uk>
Signed-off-by: Tony Lindgren <tony@atomide.com>