fbcon: fix wrong vmode bits copied on console switch

The interlaced and double line mode bits should not be copied to new
console when the console is switched.  Otherwise, the new console may be
set to incorrect refresh rate.

Also, the x and y offsets does not need to be copied.
Signed-off-by: NKrzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/video/console/fbcon.c

@@ -2275,9 +2275,7 @@ static int fbcon_switch(struct vc_data *vc)
 	 * in fb_set_var()
 	 */
 	info->var.activate = var.activate;
-	var.yoffset = info->var.yoffset;
-	var.xoffset = info->var.xoffset;
-	var.vmode = info->var.vmode;
+	var.vmode |= info->var.vmode & ~FB_VMODE_MASK;
 	fb_set_var(info, &var);
 	ops->var = info->var;