pxafb: introduce register independent LCD connection type for pxafb

Reasons:

  1. straight forward: the name "LCD_COLOR_DSTN_16BPP" is much better
     than "LCCR0_Pas | LCCR0_Color | LCCR0_Dual"

  2. by defining LCD connection types as constants, it allows only
     valid possibilities

  3. by removing the dependency of register bits definitions, those
     can be later moved into the body of pxafb.c, instead of having
     a regs-lcd.h around

Currently, only lubbock, mainstone, zylonite and littleton have been
modified to support these types (see coming patches after this).
Other platforms are encouraged to change their way describing the
LCD controller connections.

Signed-off-by: eric miao <eric.miao@marvell.com>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>