OMAP2/3 clock: drop recalc function pointers from fixed rate clocks

Now that rate recalculation and rate propagation are two separate
operations, drop recalc function pointers from all fixed rate clocks.
Their rates are fixed, so there's no need to recalculate.

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