ARM: dts: vf-colibri: increase NAND clock speed

The NAND flash memory populated on Colibri VF61 allows faster NAND
timings than the flash memory on VF50. Additionally, due to divider
limitations, VF61 did clock the flash even slower than VF50. Assign
the NFC clock in the module specific device trees vf500-colibri.dtsi
and vf610-colibri.dtsi respectively.

This increases raw read speed on Colibri VF61 by about 20%.

Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>