Add 2 more variations : FDDB28 for band 28, DEVBOARD for test purpose.

Variation DEVBOARD has no PA, we have a MCX connector for TX just after
the pre ampli, and a MCX connector for RX before the preampli.

Variation FDDB28 is for band 28 in FDD, this variation has no duplexer
on the PCB but has a MCX connector after the PA for TX and a MCX
connector for RX. The duplexer will be added outside the PCB.