lxfb: clean up register definitions

 - Rename various bitfield defines to match the data sheet names.
 - Rename DF_ register definitions to VP_ to match the data sheet;
   ie, DF_PAR -> VP_PAR.
 - for GP/DC registers, rather than defining to specific addresses, use
   an enum to number them sequentially and just multiply by 4 (bytes) to
   access them (in read_*/write_* functions).
 - for VP/FP registers, use an enum and multiple by 8 (bytes).  They're
   64bit registers.

Signed-off-by: Andres Salomon <dilinger@debian.org>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Cc: Jordan Crouse <jordan.crouse@amd.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>