net: caif: Fix debugfs on 64-bit platforms

"ser_device.state" is "unsigned long", i.e. 32-bit or 64-bit, depending
on the platform.  Hence casting its address to "u32 *", and calling
debugfs_create_x32() breaks operation on 64-bit platforms.

Fix this by using the new debugfs_create_xul() helper instead.

Fixes: 9b27105b ("net-caif-driver: add CAIF serial driver (ldisc)")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20191025094130.26033-4-geert+renesas@glider.be


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