CLK: TI: omap5: Initialize USB_DPLL at boot

USB_DPLL must be initialized and locked at boot so that
USB modules can work.

Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Tested-by: Nishanth Menon <nm@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>