clk: fixed-factor: drop round_rate() clk ops

clk: fixed-factor: drop round_rate() clk ops

This driver implements both the determine_rate() and round_rate() clk
ops, and the round_rate() clk ops is deprecated. When both are defined,
clk_core_determine_round_nolock() from the clk core will only use the
determine_rate() clk ops. Also all clk drivers that directly calls
fixed-factor's round_rate() have been migrated over to determine_rate().
So let's remove the round_rate() clk ops.

Reviewed-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Signed-off-by: Brian Masney <bmasney@redhat.com>