kfifo: fix kfifo_to_user() return type

stable inclusion
from stable-v4.19.256
commit 2cff35bb4573cbdbf1e0a405539dc9680004abe8
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5Q0SQ
CVE: NA

--------------------------------

[ Upstream commit 045ed31e23aea840648c290dbde04797064960db ]

The kfifo_to_user() macro is supposed to return zero for success or
negative error codes.  Unfortunately, there is a signedness bug so it
returns unsigned int.  This only affects callers which try to save the
result in ssize_t and as far as I can see the only place which does that
is line6_hwdep_read().

TL;DR: s/_uint/_int/.

Link: https://lkml.kernel.org/r/YrVL3OJVLlNhIMFs@kili


Fixes: 144ecf31 ("kfifo: fix kfifo_alloc() to return a signed int value")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Stefani Seibold <stefani@seibold.net>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>