OMAP3: set the core dpll clk rate in its set_rate function

The debug l3_ick/rate is not displaying the actual rate of the clock in
hardware. This is because, the core dpll set_rate function doesn't update the
clk.rate. After fixing, the l3_ick/rate is displaying proper values.

Signed-off-by: Shweta Gulati <shweta.gulati@ti.com>
Signed-off-by: Avinash.H.M <avinashhm@ti.com>
Cc: Rajendra Nayak <rnayak@ti.com>
Cc: Paul Wamsley <paul@pwsan.com>
Acked-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>