ARM: dts: at91: Remove the USB EP child node

The endpoint configuration used to be stored in the device tree,
however the configuration depend on the "version" of the controller
itself.

Then the EP child node are useless and describe as deprecated in the
documentation binding: remove all the nodes from the SoC device tree
file. Remove also the #address-cells and #size-cells properties that
are no longer needed.

Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>