[mcs814x] add Moschip MSC814x support

This target currently only supports Moschip's MCS8140 SoC, but support
for other chips in the same family (MCS8142, MCS8144) will be easy to add.

Target support is entirely using Device Tree for probing peripherals.
Drivers support include:
- PCI
- USB 1 & 2
- watchdog
- random number generator
- UART
- timer
- internal Ethernet PHY
- Ethernet MAC core

Support for the following boards is included using Device Tree
- Devolo dLAN USB Extender
- Tigal RBT-832

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@32462 3c298f89-4303-0410-b956-a3cf2f4a3e73