OMAPDSS: cleanup probe functions

Now that dss is using devm_ functions for allocation in probe functions,
small reordering of the allocations allows us to clean up the probe
functions more.

This patch moves "unmanaged" allocations after the managed ones, and
uses plain returns instead of gotos where possible. This lets us remove
a bunch of goto labels, simplifying the probe's error handling.

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