io_uring: Fix unsigned 'res' comparison with zero in io_fixup_rw_res()

stable inclusion
from stable-v5.10.163
commit 07b3672c4090d1e8147b1ae9c2546d8a8d8e13ae
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7PJ9N

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=07b3672c4090d1e8147b1ae9c2546d8a8d8e13ae



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Smatch warning: io_fixup_rw_res() warn:
	unsigned 'res' is never less than zero.

Change type of 'res' from unsigned to long.

Fixes: d6b7efc722a2 ("io_uring/rw: fix error'ed retry return values")
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: zhaoxiaoqiang11 <zhaoxiaoqiang11@jd.com>