Accton AS7700_32X: Resize diag partition to 32MB

Signed-off-by: Curt Brune <curt@cumulusnetworks.com>
docs:  added details for Ethernet management configuration

Spelled out the details of how the Ethernet management port IP address
is configured.
BCM PHY patch: correct copyright notice

I had the copyright notice wrong on this patch.
Accton AS6701_32X: Remove unavailable usb node from DTS

The USB node ``usb@23000`` never exists in the box.  It should
remove the node from DTS directly rather than by u-boot at
runtime.
Accton platforms: Revise 'onie_sz.b' to 0x500000

The platforms are including:
- AS5710_54X
- AS6700_32X
- AS6701_32X
- AS6710_32X
- AS7700_32X

To speed up booting into ONIE, we decide to revise 'onie_sz.b' to
0x500000 for all powerpc platforms except AS4600_54T, AS5600_52X,
and AS5610_52X.