Fix decoding for the NX300

The SRW decoding method didn't include the final red/blue swap present in dcraw. Not doing the swap and setting the CFA pattern accordingly generates red/blue fringing. An example file that shows this:

https://encrypted.pcode.nl/files/temp/07220006.SRW

The simple solution is to do a final swap of the red/blue pixels and change the CFA pattern to match. There may be a better way of doing it though, that doesn't require the extra step.