clk: Don't write error code into divider register

Add a check for error returned by divider value calculation to avoid
writing error code into hw register.

Signed-off-by: Alex Frid <afrid@nvidia.com>
Reviewed-by: Peter De Schrijver <pdeschrijver@nvidia.com>
Reviewed-by: Jon Mayo <jmayo@nvidia.com>
Fixes: bca9690b ("clk: divider: Make generic for usage elsewhere")
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>