ARM: OMAP3+: dpll: use DPLL's round_rate when setting rate

omap3_noncore_dpll_set_rate uses omap2_dpll_round_rate explicitly.  Instead
use the struct clk pointer's round_rate function to allow for DPLL's with
special needs.

An example of a clock that requires this is DPLL_ABE on OMAP4 which
can have a 4x multiplier on top of the usual MN dividers depending on
register settings.  This requires a special round_rate function that
might yield a rate different from the initial target.

Signed-off-by: Mike Turquette <mturquette@ti.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>
[paul@pwsan.com: split rate assignment portion into a separate patch]
Signed-off-by: Paul Walmsley <paul@pwsan.com>