OMAP: CLK: CLKSRC: Add suspend resume hooks

Add the save and restore for clksrc as part of suspend and resume
so that it saves the counter value and restores. This is needed in
modes like rtc+ddr in self-refresh not doing this stalls the time.

Signed-off-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>