Corrected range mismatch (DSCP values vs. raw values in the TOS byte)

Existing code assumes that DSCP values are always already shifted two bits to left - with a tiny, yet potentially fatal exception in three lines.

http://forum.pfsense.org/index.php/topic,63580.0.html
Merge pull request #127 from Klaws--/patch-2

Corrected range mismatch (DSCP values vs. raw values in the TOS byte)