ARM: dts: k2e-evm: add 1g ethernet phys nodes

Keystone K2E-EVM has two 1G Marvell 88E1514 Ethernet PHYs
installed, which are compatible with 88E1510.
Hence, add corresponding child nodes for 1G MDIO bus.

For more information see:
  https://www.einfochips.com/index.php/partnerships/texas-instruments/k2e-evm.html

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Santosh Shilimkar <ssantosh@kernel.org>