ARM: OMAP3+: DPLL: use determine_rate() and set_rate_and_parent()

Currently, DPLLs are hiding the gory details of switching parent
within set_rate, which confuses the common clock code and is wrong.
Fixed by applying the new determine_rate() and set_rate_and_parent()
functionality to any clock-ops previously using the broken approach.
This patch also removes the broken legacy code.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>