drm/omap: DMM: Fix DMM_IRQSTAT_ERR_MASK definition

The error bit definitions are typoed in DMM_IRQSTAT_ERR_MASK which went
unnoticed since the DMM_IRQSTAT_ERR_MASK was not used.

Change the bit definitions to the correct ones.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>