MIPS: BMIPS: Improve BCM6328 device tree

MIPS: BMIPS: Improve BCM6328 device tree

- Remove unneeded leds0 alias.
- Switch to bcm6345-l1-intc interrupt controller.
- Use interrupt-controller instead of periph_intc and cpu_intc.
- Add uart1, ehci and ohci nodes.
- Refactor syscon and syscon-reboot.
- Avoid using underscores in node names.
- Rename uart aliases to serial.

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Cc: f.fainelli@gmail.com
Cc: jogo@openwrt.org
Cc: cernekee@gmail.com
Cc: robh@kernel.org
Cc: simon@fire.lp0.eu
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Cc: devicetree@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/13043/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>