debugfs: remove return value of debugfs_create_u32()

No one checks the return value of debugfs_create_u32(), as it's not
needed, so make the return value void, so that no one tries to do so in
the future.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20200416145448.GA1380878@kroah.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>