MIPS: bcm3384: Initial commit of bcm3384 platform support

MIPS: bcm3384: Initial commit of bcm3384 platform support

This supports SMP Linux running on the BCM3384 Zephyr (BMIPS5000)
application processor, with fully functional UART and USB 1.1/2.0.
Device Tree is used to configure the following items:

 - All peripherals
 - Early console base address
 - SMP or UP mode
 - MIPS counter frequency
 - Memory size / regions
 - DMA offset
 - Kernel command line

The DT-enabled bootloader and build instructions are posted at
https://github.com/Broadcom/aeolus

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Cc: f.fainelli@gmail.com
Cc: mbizon@freebox.fr
Cc: jogo@openwrt.org
Cc: jfraser@broadcom.com
Cc: linux-mips@linux-mips.org
Cc: devicetree@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/8170/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>