[Code coverage]: Fix the issue of function code coverage in device.c.

It was reported in the code coverage report that Z_SYSCALL_HANDLER() was
not called by other code, if we run "sanitycheck -p qemu_x86 --coverage
-T tests/kernel/device/".

The root cause is that we include "errno.h", which includes
"include/generated/syscalls/device.h". It causes that the
declare of device_get_binding() in "include/generated/syscalls/device.h"
is marked as "has been called", rather than Z_SYSCALL_HANDLER()
in device.c.

So I remove "#include <errno.h>", which is useless in device.c. Also,
"#include <sys/util.h>" is removed for the same reason.

Signed-off-by: Steven Wang <steven.l.wang@linux.intel.com>