video/udlfb: fix line counting in fb_write

Line 0 and 1 were both written to line 0 (on the display) and all subsequent
lines had an offset of -1. The result was that the last line on the display
was never overwritten by writes to /dev/fbN.

Cc: stable@vger.kernel.org
Signed-off-by: NAlexander Holler <holler@ahsoftware.de>
Acked-by: NBernie Thompson <bernie@plugable.com>
Signed-off-by: NFlorian Tobias Schandinat <FlorianSchandinat@gmx.de>

drivers/video/udlfb.c

@@ -647,7 +647,7 @@ static ssize_t dlfb_ops_write(struct fb_info *info, const char __user *buf,
 	result = fb_sys_write(info, buf, count, ppos);
 
 	if (result > 0) {
-		int start = max((int)(offset / info->fix.line_length) - 1, 0);
+		int start = max((int)(offset / info->fix.line_length), 0);
 		int lines = min((u32)((result / info->fix.line_length) + 1),
 				(u32)info->var.yres);