Fix `make depend` in sys/modules/otus

[lwhsu]

Summary

Fix make depend error in sys/modules/otus:

$ make depend
machine -> /usr/home/lwhsu/work/freebsd-src/head/sys/amd64/include
x86 -> /usr/home/lwhsu/work/freebsd-src/head/sys/x86/include
:> opt_bus.h
:> opt_usb.h
awk -f /usr/home/lwhsu/work/freebsd-src/head/sys/modules/otus/../../tools/usbdevs2h.awk /usr/home/lwhsu/work/freebsd-src/head/sys/modules/otus/../../dev/usb/usbdevs -h
rm -f .depend
mkdep -f .depend -a   -nostdinc -D_KERNEL -DKLD_MODULE -I. -I/usr/home/lwhsu/work/freebsd-src/head/sys/modules/otus/../.. -std=iso9899:1999 -std=iso9899:1999   /usr/home/lwhsu/work/freebsd-src/head/sys/modules/otus/../../dev/otus/if_otus.c
/usr/home/lwhsu/work/freebsd-src/head/sys/modules/otus/../../dev/otus/if_otus.c:27:10: fatal error: 'opt_wlan.h' file not found
#include "opt_wlan.h"
         ^
1 error generated.
mkdep: compile failed
*** Error code 1

Stop.
make: stopped in /usr/home/lwhsu/work/freebsd-src/head/sys/modules/otus

Test Plan

cd sys/modules/otus; make depend