target: Use a PASSTHROUGH flag instead of transport_types

It seems like we only care if a transport is passthrough or not. Convert
transport_type to a flags field and replace TRANSPORT_PLUGIN_* with a
flag, TRANSPORT_FLAG_PASSTHROUGH.

Signed-off-by: Andy Grover <agrover@redhat.com>
Reviewed-by: Ilias Tsitsimpis <iliastsi@arrikto.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
index 2768ea2..07d2996 100644
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c
@@ -1077,7 +1077,7 @@
 	.inquiry_prod		= "USER",
 	.inquiry_rev		= TCMU_VERSION,
 	.owner			= THIS_MODULE,
-	.transport_type		= TRANSPORT_PLUGIN_PHBA_PDEV,
+	.transport_flags	= TRANSPORT_FLAG_PASSTHROUGH,
 	.attach_hba		= tcmu_attach_hba,
 	.detach_hba		= tcmu_detach_hba,
 	.alloc_device		= tcmu_alloc_device,