scsi: drivers: base: Support atomic version of attribute_container_device_trigger

scsi: drivers: base: Support atomic version of attribute_container_device_trigger

attribute_container_device_trigger invokes callbacks that may fail for one
or more classdevs, for instance, the transport_add_class_device callback,
called during transport creation, does memory allocation.  This
information, though, is not propagated to upper layers, and any driver
using the attribute_container_device_trigger API will not know whether any,
some, or all callbacks succeeded.

This patch implements a safe version of this dispatcher, to either succeed
all the callbacks or revert to the original state.

Link: https://lore.kernel.org/r/20200106185817.640331-2-krisman@collabora.com
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>