clk: uniphier: fix memory overrun bug

The first loop of this "for" statement writes memory beyond the
allocated clk_hw_onecell_data.

It should be:
    for (clk_num--; clk_num >= 0; clk_num--)
            ...

Or more simply:
    while (--clk_num >= 0)
            ...

Fixes: 734d82f4

 ("clk: uniphier: add core support code for UniPhier clock driver")
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>