vt/consolemap: do font sum unsigned

[ Upstream commit 9777f8e ]

The constant 20 makes the font sum computation signed which can lead to
sign extensions and signed wraps. It's not much of a problem as we build
with -fno-strict-overflow. But if we ever decide not to, be ready, so
switch the constant to unsigned.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210105120239.28031-7-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/tty/vt/consolemap.c

@@ -495,7 +495,7 @@ con_insert_unipair(struct uni_pagedir *p, u_short unicode, u_short fontpos)
 
 	p2[unicode & 0x3f] = fontpos;
 
-	p->sum += (fontpos << 20) + unicode;
+	p->sum += (fontpos << 20U) + unicode;
 
 	return 0;
 }