ARM: OMAP2+: Add DPPLS clock manager for dm814x

On dm814x we have some clocks at DPLLS and some at PRCM. Let's add a new
omap_prcm_init_data entry for the DPLLS so we can initalize timer clocks
early.

Cc: Paul Walmsley <paul@pwsan.com>
Cc: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>