OMAP: WDT: Use PM runtime APIs instead of clk FW APIs

Call runtime pm APIs pm_runtime_put_sync() and pm_runtime_get_sync()
for enabling/disabling the clocks, sysconfig settings instead of using
clock FW APIs.

Signed-off-by: Charulatha V <charu@ti.com>
Acked-by: Cousson, Benoit <b-cousson@ti.com>
Acked-by: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>