clk: imx: remove redundant initialization of ret to zero

The initialization of ret is redundant as it is being re-assigned to
the return value from the call to imx8m_clk_composite_compute_dividers.
Clean this up by removing the initialization.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>