If the dpll is already locked, code can be optimized
to return much earlier than doing redundent set of lock mode
and wait on idlest.

Cc: Tony Lindgren <tony@atomide.com>
Cc: Jon Hunter <jon-hunter@ti.com>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Mike Turquette <mturquette@ti.com>
Signed-off-by: NVikram Pandita <vikram.pandita@ti.com>
Signed-off-by: NNishanth Menon <nm@ti.com>
Signed-off-by: NPaul Walmsley <paul@pwsan.com>