ARM: dts: Add Aspeed SoC USB controllers to device-tree

This adds the USB controllers to the DT template of the
AST24xx and AST25xx SoCs.

This patch doesn't enable them by default on any board specific
.dts yet. This will be done when we have the necessary clock/reset
and pinmux support. In the meantime though, this will work if
u-boot configures things properly.

For the AST2400 I only added pinmux definition for port 1
which is dual USB1/USB2. There are additional USB1 only ports
that might require more work but I don't have HW to test at
hand so I'm leaving that to whoever cares.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reviewed-by: Andrew Jeffery <andrew@aj.id.au>
Signed-off-by: Joel Stanley <joel@jms.id.au>