vfio: Remove superfluous error report in vfio_listener_region_add()

vfio: Remove superfluous error report in vfio_listener_region_add()

For pseries machines, commit 567b5b309abe ("vfio/pci: Relax DMA map
errors for MMIO regions") introduced 2 error reports to notify the
user of MMIO mapping errors. Consolidate both code paths under one.

Cc: Harsh Prateek Bora <harshpb@linux.ibm.com>
Cc: Shivaprasad G Bhat <sbhat@linux.ibm.com>
Reviewed-by: Harsh Prateek Bora <harshpb@linux.ibm.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20250206131438.1505542-8-clg@redhat.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>