arm: vt8500: Add wm8850 config options to multi_v7_defconfig

This patch finally adds the WM8850 SoC to the multi_v7_defconfig.
We don't have a seperate defconfig for this SoC as it is only
available as a multiplatform option.

Signed-off-by: Tony Prisk <linux@prisktech.co.nz>
Signed-off-by: Olof Johansson <olof@lixom.net>