ARM: dts: dra7: Add CPSW and MDIO module nodes for dra7

Add CPSW and MDIO related device tree data for DRA7XX and made as status
disabled. Phy-id, pinmux for active and sleep state needs to be added in
board dts files and enable the CPSW device.

[cherry-picked from https://patchwork.kernel.org/patch/5112431/ ]
Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
ARM: dts: am57xx-beagle-x15: Add dual ethernet

Make CPSW work - BeagleBoard-X15 has two network ports

MUX_MODE15 means "driver off". Pins are turned off
conserving more power.

Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>