pseries: Fix bug with reset of VIO CRQs

pseries: Fix bug with reset of VIO CRQs

PAPR specifies a Command Response Queue (CRQ) mechanism used for virtual
IO, which we implement.  However, we don't correctly clean up registered
CRQs when we reset the system.

This patch adds a reset handler to fix this bug.  While we're at it, add
in some of the extra debug messages that were used to track the problem
down.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
[AF: Updated hcall_dprintf()s to not duplicate the function name]
Signed-off-by: Andreas Färber <afaerber@suse.de>