OMAP clock: move rate recalc, propagation code up to plat-omap/clock.c

Previously the individual clock recalculation functions handled their
own rate recalculation.  This can be handled in the clk_set_rate(),
clk_set_parent(), and recalculate_root_clocks() functions in
plat-omap/clock.c.  Removes duplicate code and clarifies the role of the
recalc functions.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>