bus: ti-sysc: Fix optional clocks array access

We should be checking ddata->clocks[i] instead of clock_names[i]
for the optional clocks. Currently this just happens to work for
the typical case of one fck and one optional clock.

Fixes: 09dfe581 ("bus: ti-sysc: Add handling for clkctrl opt clocks")
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>