Fix `make depend` in sys/modules

[lwhsu]

Summary

Without this, make depend in sys/modules generates this error:

===> sys/modules/cryptodev (depend)
machine -> /jenkins/workspace/FreeBSD_HEAD-scan-build/src/sys/amd64/include
x86 -> /jenkins/workspace/FreeBSD_HEAD-scan-build/src/sys/x86/include
awk -f /jenkins/workspace/FreeBSD_HEAD-scan-build/src/sys/modules/cryptodev/../../tools/makeobjops.awk /jenkins/workspace/FreeBSD_HEAD-scan-build/src/sys/modules/cryptodev/../../kern/bus_if.m -h
awk -f /jenkins/workspace/FreeBSD_HEAD-scan-build/src/sys/modules/cryptodev/../../tools/makeobjops.awk /jenkins/workspace/FreeBSD_HEAD-scan-build/src/sys/modules/cryptodev/../../kern/device_if.m -h
:> opt_compat.h
rm -f .depend
CC='/jenkins/workspace/FreeBSD_HEAD-scan-build/obj/jenkins/workspace/FreeBSD_HEAD-scan-build/src/tmp/usr/bin/cc -target x86_64-unknown-freebsd11.0 ' mkdep -f .depend -a   -nostdinc -D_KERNEL -DKLD_MODULE -I. -I/jenkins/workspace/FreeBSD_HEAD-scan-build/src/sys/modules/cryptodev/../.. -I/jenkins/workspace/FreeBSD_HEAD-scan-build/src/sys/modules/cryptodev/../../contrib/altq -std=iso9899:1999   /jenkins/workspace/FreeBSD_HEAD-scan-build/src/sys/modules/cryptodev/../../opencrypto/cryptodev.c
/jenkins/workspace/FreeBSD_HEAD-scan-build/src/sys/modules/cryptodev/../../opencrypto/cryptodev.c:45:10: fatal error: 'opt_kdtrace.h' file not found
#include "opt_kdtrace.h"
         ^
1 error generated.
mkdep: compile failed
*** Error code 1

Test Plan

cd sys/modules; make depend

[lwhsu]

Closed by commit rS275931 (authored by @lwhsu).