ARM: BCM5301X: add NAND flash chip description for Asus RT-AC87U

ARM: BCM5301X: add NAND flash chip description for Asus RT-AC87U

The NAND flash chip description were not imported for the Asus RT-AC87U
dts file when this was done for all the other dts files, because these
patches were send in parallel.

This adds a missing NAND flash chip description to this patch:
commit 9faa5960eef3204cae6637b530f5e23e53b5a9ef
Author: Hauke Mehrtens <hauke@hauke-m.de>
Date: Fri May 29 23:39:47 2015 +0200

ARM: BCM5301X: add NAND flash chip description

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>