fix CRC7 implementation

I have been trying to add CRC7 checking to this analyzer (along with exporting), and I have not been able to make the CRC7 implementation work.

I had the analyzer generate some simulated data, and the CRC's differ from what valid data should be.

CMD0 with arg=0 should produce CRC value 0x4A, but the simulated data produces CRC value 0x49

The fixed code was taken from here
http://www.humblesoft.com/n-card/kernel-patch-2.4.21-pre4/mmc-driver.txt