UIO: fix up inapposite whiteplace in uio head file

Whitespace is used in the inapposite place,
which makes checkpatch complain.
Signed-off-by: Qiang Su <suqiang4@huawei.com>
Link: https://lore.kernel.org/r/20200306070359.71398-1-suqiang4@huawei.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>