clk: stm32: stm32-core: convert from divider_ro_round_rate() to divider_ro_determine_...

clk: stm32: stm32-core: convert from divider_ro_round_rate() to divider_ro_determine_rate()

The divider_ro_round_rate() function is now deprecated, so let's migrate
to divider_ro_determine_rate() instead so that this deprecated API can
be removed.

Note that when the main function itself was migrated to use
determine_rate, this was mistakenly converted to:

    req->rate = divider_round_rate(...)

This is invalid in the case when an error occurs since it can set the
rate to a negative value.

Fixes: cd1cb38836c0 ("clk: stm32: stm32-core: convert from round_rate() to determine_rate()")
Signed-off-by: Brian Masney <bmasney@redhat.com>