clk: versatile-icst: fix memory leak

A static code checker found a memory leak in the Versatile
ICST code. Fix it.

Fixes: a183da63

 "clk: versatile: respect parent rate in ICST clock"
Reported-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>