[Open-graphics] More on video controller

[Timothy Normand Miller]

I've modified progressive.asm and vcntrl_asm.h to match the
documentation.  There's now a parameter to indicate how many pixels
per clock get transmitted (2 instead of 4 for single-link DVI).  The
way operands for INC instructions were being computed was wrong, so I
fixed that too.  Together, this required me to move some scaling
factors out of vcntrl_asm.h and make them explicit in the asm code.

-- 
Timothy Normand Miller
http://www.cse.ohio-state.edu/~millerti
Favorite book:  The Design of Everyday Things, Donald A. Norman, ISBN
0-465-06710-7