drm/tidss: Add printing of underflows

Add printing of underflows the same way as we handle sync losts.

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-v1-4-82ddaec94e4a@ideasonboard.com