DA830 EVM: MUSB platform code

Properly set up the OTG mode thru the CFGCHIP2 register, enable the
USB0_DRVVBUS pin, and finally register the MUSB platform device.

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>