ODROID: gps: Support configurable GPS settings by system prop.

"ro.kernel.android.gps" specify the device node to access GPS module,
"ro.kernel.android.gps.speed" specify the *baudrate* to read from GPS.
Since certain vendor's GPS module support different baudrate like 4800.

"dev/ttyACM0" and "9600" baudrate will be used as default if required properties
are missing.

Change-Id: I03db6c5c45d49ccb944f997a936ace2ab0e7a1bd