arm: vybrid: Update defconfig's

Let's go with pure DT solution for board's
based on NXP/Freescale Vybrid platform.

- Merge the DT defconfig with non-DT defconfig for Toradex
  Colibri VF50/VF61 and drop the non-DT defconfig.
- Update the legacy defconfigs for NXP/Freescale VF610 Tower
  Board with DT.
- Update the legacy defconfigs for Phytec phyCORE-vybrid
  Board with DT.

Signed-off-by: Bhuvanchandra DV <bhuvanchandra.dv@toradex.com>
Acked-by: Stefan Agner <stefan.agner@toradex.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>