OMAP3+: SR: enable/disable SR only on need

Since we already know the state of the autocomp enablement, we can
see if the requested state is different from the current state and
enable/disable SR only on the need basis.

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>