s3c2410fb: adds pixclock to s3c2410fb_display

This patch adds pixelclock field to the s3c2410fb_display structure and make
use of it in the driver.

The Bast machine defined 9 modes but pixclock and margin values are defined
only for the 640x480 modes so I removed other modes.

This patch also fixes wrong display type constant for the SMDK2440 board.

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>