clk: iproc: fix memory leak from clock name

of_property_read_string_index takes array of pointers and assign them to
strings read from device tree property. No additional memory allocation
is needed prior to calling of_property_read_string_index. In fact, since
the array of pointers will be re-assigned to other strings, any memory
that it points to prior to calling of_property_read_string_index will be
leaked

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Ray Jui <rjui@broadcom.com>
Fixes: 5fe225c1 ("clk: iproc: add initial common clock support")
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>