OMAP: DSS2: Taal: Change ESD work management

Move ESD work queuing and cancelling out of taal_power_on/off() to avoid
problems related to taal_esd_work() calling the power on/off functions.

Signed-off-by: Jani Nikula <ext-jani.1.nikula@nokia.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@nokia.com>