Cleaning vgaWriteScan( )

The following patch cleans the vgaWriteScan ( ) in Vga driver:
http://doxygen.reactos.org/d1/d52/vgavideo_8c_source.html#l00654
If cleans the following assignments:

dummy = vp[off];
dummy = bp[i];
vp[off] = dummy;

to:
vp[off]= bp[i];

And also removes "dummy" variable which was just used for this.