OMAPDSS: DISPC: remove dssdev depependency from error handler

The dispc error handler tries to "fix" issues by disabling and enabling
panel. This is problematic, as we're trying to remove the dependency
from omapdss to the omap_dss_devices. It's also racy, and doesn't really
fix anything.

This patch removes the use of omap_dss_device from the error handler,
and just disables and enables the associated overlay manager. This
should produce similar results as the previous solution, without using
dssdev.

However, the error handling is still horrible. But the problem boils
down to one question, to which I don't have a clear answer: what to do
when a HW error happens?

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>