ARM: dts: sa2150p: add dt for ethernet phy

The sa2150p and remote processor will be connected
through ethernet. This commit adds device tree
for ethernet PHY use-case.

Change-Id: If50bb725c2a113c7aeb52e511393e12761da20ca
Signed-off-by: Rishi Gupta <rishgupt@codeaurora.org>