clk: microchip: core: remove duplicate roclk_determine_rate()

Fix compiler error caused by the round_rate() to determine_rate()
migration.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202509280327.jsapR0Ww-lkp@intel.com/


Signed-off-by: Brian Masney <bmasney@redhat.com>
Fixes: e9f039c0 ("clk: microchip: core: convert from round_rate() to determine_rate()")
Signed-off-by: Stephen Boyd <sboyd@kernel.org>