sunxi: add kitchensink to defconfig.

Compile tested.

Contains most stuff you could possibly connect to a sunxi - devices
conecting through USB, Ethernet, SPI, I2C.

- remove a[12] configs
- add sun5i_nuclear and sun[45]i_headless configs

- add branch optimization

Not configured/unavalable:
- netconsole over USB - the USB gadget is not capable enough
- serial console over USB serial - needs compiled in USB serial drivers
- numerous filesystems are not included