s3c2410_fb: fix line length calculation

Fix line length calculation. var->width is the size of the display in mm. We
like to use the pixel size.

Without this fix, dynamic (fbset) based resolution and depths changes with
s3c2410_fb don't work at all.

Spotted by john cass <johnpcass@yahoo.com>

Signed-off-by: Stefan Schmidt <stefan@openmoko.org>
Signed-off-by: Harald Welte <laforge@openmoko.org>
Acked-by: Ben Dooks <ben-linux@fluff.org>
Acked-by: Arnaud Patard <arnaud.patard@rtp-net.org>
Acked-by: Krzysztof Helt <krzysztof.h1@wp.pl>
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@akpm@linux-foundation.org>