clk: ti: dpll: convert from round_rate() to determine_rate()

The round_rate() clk ops is deprecated, so migrate this driver from
round_rate() to determine_rate(). Part of these changes were done
using the Coccinelle semantic patch on the cover letter of this
series, and the rest of the changes were manually done.

omap4_dpll_regm4xen_round_rate() is now only called by
omap4_dpll_regm4xen_determine_rate(), so let's merge that functionality
into one function. This is needed for another cleanup to completely
remove the round_rate() clk ops from the clk core.

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>