xen/pciback: miscellaneous adjustments

This is a minor bugfix and a set of small cleanups; as it is not clear
whether this needs splitting into pieces (and if so, at what
granularity), it is a single combined patch.
- add a missing return statement to an error path in
  kill_domain_by_device()
- use pci_is_enabled() rather than raw atomic_read()
- remove a bogus attempt to zero-terminate an already zero-terminated
  string
- #define DRV_NAME once uniformly in the shared local header
- make DRIVER_ATTR() variables static
- eliminate a pointless use of list_for_each_entry_safe()
- add MODULE_ALIAS()
- a little bit of constification
- adjust a few messages
- remove stray semicolons from inline function definitions

Signed-off-by: Jan Beulich <jbeulich@suse.com>
[v1: Dropped the resource_size fix, altered the description]
[v2: Fixed cleanpatch.pl comments]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
diff --git a/drivers/xen/xen-pciback/passthrough.c b/drivers/xen/xen-pciback/passthrough.c
index e01e4b6..828dddc 100644
--- a/drivers/xen/xen-pciback/passthrough.c
+++ b/drivers/xen/xen-pciback/passthrough.c
@@ -176,7 +176,7 @@
 	return 1;
 }
 
-struct xen_pcibk_backend xen_pcibk_passthrough_backend = {
+const struct xen_pcibk_backend xen_pcibk_passthrough_backend = {
 	.name           = "passthrough",
 	.init           = __xen_pcibk_init_devices,
 	.free		= __xen_pcibk_release_devices,