lantiq: added support for VPE1

lantiq: added support for VPE1

Created minimal patchset based on BB rev 43158 by Eddi De Pieri
14.07/openwrt.git 79472c025449efae9310defad0d3a73cff14d756

If the VR9 based router provides FXS ports and they shoud enabled then
the following must added to the kernel command line:
mem=[TOTALMEMSIZE-2M] vpe1_load_addr=ADDRESS vpe1_mem=2M maxvpes=1
maxtcs=1

To use FXS 2M of RAM are needed for the VPE firmware. The size is set
by vpe1_mem.
The available RAM must be reduced by this size using the mem argument.
A correct load address (example 0x83e00000) for the firmware must be given,
too.

Signed-off-by: Stefan Koch <stefan.koch10@gmail.com>