clk: mediatek: Fix memory leak on clock init fail

mtk_clk_register_composite() may leak memory due to some error
handling path don't free all allocated memory. This patch
free all pointers that may allocate memory before error return.
And it's safe because kfree() can handle NULL pointers.

Signed-off-by: James Liao <jamesjj.liao@mediatek.com>
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>