cirrusfb: code improvement 2nd part

This patch removes:
- redundant fields from the cirrusfb_regs structure
- one redundant header
- fixes two includes ("" to <>)

Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Antonino Daplas <adaplas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>