clk: ti: dpll: remove round_rate() in favor of determine_rate()

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, so let's remove the round_rate() clk ops since
it's unused.

Tested-by: Anddreas Kemnade <andreas@kemnade.info> # OMAP3 GTA04, OMAP4 Panda
Reviewed-by: Kevin Hilman <khilman@baylibre.com>
Tested-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Brian Masney <bmasney@redhat.com>