board/BuR/brppt1: fix ethernet support on brppt1 boards

The commit 1bac199e ("configs: Resync with savedefconfig")
did remove ethernet driver from following boards defconfig:

- brppt1_mmc
- brppt1_nand
- brppt1_spi

With this commit we add ethernet and responsible phy support again.

Signed-off-by: Hannes Schmelzer <hannes.schmelzer@br-automation.com>