lantiq: BTHOMEHUBV5A - explicit select the flash device

The stock u-boot doesn't disable unused flash banks. Therefore, the nand
driver tries to initialize a not connected NOR flash and the device
hangs on boot.

Workaround the issue by selecting the second flash bank (NAND).

Signed-off-by: Mathias Kresin <openwrt@kresin.me>
Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>

SVN-Revision: 48657