OMAP: DSS2: Taal: Ensure panel is enabled in enable_te() and run_test()

Bail out from taal_enable_te() and taal_run_test() if panel is not
enabled.

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