div64: Don't instrument the division function

This function may be called from tracing code, since that code needs to
read the timer and this often requires calling do_div(), which calls
__div64_32(). If this function is instrumented it causes an infinite loop,
since emitting a trace record requests the time, which in turn emits a
trace record, etc.

Update the prototype to prevent instrumentation code being added.

Signed-off-by: Simon Glass <sjg@chromium.org>