Revert "ARC: [plat-axs10x] add Ethernet PHY description in .dts"

This reverts commit 667a490b.

This is needed to get ethernet(stmmac) working in 4.6-rc2 on axs103.

4.5 needed this fix, but apprently stmmac has gained some fixes which
warrant reversal of this.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>