hw/ppc/spapr_drc: Replace error_setg(&error_abort) by error_report() + abort()

hw/ppc/spapr_drc: Replace error_setg(&error_abort) by error_report() + abort()

Use error_report() + abort() instead of error_setg(&error_abort),
as suggested by the "qapi/error.h" documentation:

    Please don't error_setg(&error_fatal, ...), use error_report() and
    exit(), because that's more obvious.
    Likewise, don't error_setg(&error_abort, ...), use assert().

Use abort() instead of the suggested assert() because the error message
already got displayed.

Suggested-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>