fbcon: fix monochrome color value calculation

commit 08650869 upstream

Commit 22af89aa ("fbcon: replace mono_col
macro with static inline") changed the order of operations for computing
monochrome color values.  This generates 0xffff000f instead of 0x0000000f
for a 4 bit monochrome color, leading to image corruption if it is passed
to cfb_imageblit or other similar functions.  Fix it up.

Cc: Harvey Harrison <harvey.harrison@gmail.com>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/video/console/fbcon.h

@@ -110,7 +110,7 @@ static inline int mono_col(const struct fb_info *info)
 	__u32 max_len;
 	max_len = max(info->var.green.length, info->var.red.length);
 	max_len = max(info->var.blue.length, max_len);
-	return ~(0xfff << (max_len & 0xff));
+	return (~(0xfff << max_len)) & 0xff;
 }
 
 static inline int attr_col_ec(int shift, struct vc_data *vc,