drm/tidss: Remove unused OCP error flag

We never use the DSS_IRQ_DEVICE_OCP_ERR flag, and the HW doesn't even
have such a bit... So remove it.

Reviewed-by: Devarsh Thakkar <devarsht@ti.com>
Reviewed-by: Aradhya Bhatia <aradhya.bhatia@linux.dev>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241021-tidss-irq-fix-v1-2-82ddaec94e4a@ideasonboard.com