emacps: Add gmii2rgmii converter support

If the gmii2rgmii converter is used and connect to the ps7 ethernet,
add "gmii2rgmii-phy-handle" property and create phy node under mdio node.

Signed-off-by: Jason Wu <j.wu@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
slcr: Detect ps-clk-frequency dynamically

Since the input crystal clock frequency is exported in 2014.3, we can
detect the ps-clk-frequency dynamically.

Signed-off-by: Jason Wu <j.wu@xilinx.com>
dmaps: Do not generate periphid

ID is not required by the Linux kernel.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>