arm: atmel: add gmac support for sama5d3xek board

add gmac support for sama5d3xek board, the gmac embedded in:
  - sama5d33, sama5d34, sama5d35

Signed-off-by: Bo Shen <voice.shen@atmel.com>
Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>
4 files changed