Add bootph-all tag to phy_gmii_sel node. This is needed for booting via
Ethernet. While at it, drop main_pktdma reg redefinitions which are already
provided by the top-level SoC device tree file.
Signed-off-by: Wadim Egorov <w.egorov@phytec.de> Tested-by: Daniel Schultz <d.schultz@phytec.de>