OMAP2+: PM: Initialise sleep_switch to a non-valid value

sleep_switch which is initialised to 0 in omap_set_pwrdm_state
happens to be a valid sleep_switch type (FORCEWAKEUP_SWITCH)
which are defined as:

 #define FORCEWAKEUP_SWITCH      0
 #define LOWPOWERSTATE_SWITCH    1

This causes the function to wrongly program some clock domains
even when the Powerdomain is in ON state.

Signed-off-by: Rajendra Nayak <rnayak@ti.com>
Cc: Paul Walmsley <paul@pwsan.com>
Acked-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>