ptp: ocp: Make debugfs variables the correct bitwidth

An earlier patch mistakenly changed these variables from u32 to u16,
leading to unintended truncation.  Restore the original logic.

Fixes: a509a7c6

 ("ptp: ocp: Add support for selectable SMA directions.")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Link: https://lore.kernel.org/r/20220316165347.599154-1-jonathan.lemon@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>