virtio_blk: eliminate anonymous module_init & module_exit

Eliminate anonymous module_init() and module_exit(), which can lead to
confusion or ambiguity when reading System.map, crashes/oops/bugs,
or an initcall_debug log.

Give each of these init and exit functions unique driver-specific
names to eliminate the anonymous names.

Example 1: (System.map)
 ffffffff832fc78c t init
 ffffffff832fc79e t init
 ffffffff832fc8f8 t init

Example 2: (initcall_debug log)
 calling  init+0x0/0x12 @ 1
 initcall init+0x0/0x12 returned 0 after 15 usecs
 calling  init+0x0/0x60 @ 1
 initcall init+0x0/0x60 returned 0 after 2 usecs
 calling  init+0x0/0x9a @ 1
 initcall init+0x0/0x9a returned 0 after 74 usecs

Fixes: e467cde ("Block driver using virtio.")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: virtualization@lists.linux-foundation.org
Cc: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Link: https://lore.kernel.org/r/20220316192010.19001-2-rdunlap@infradead.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/virtio_blk.c

@@ -1022,7 +1022,7 @@ static struct virtio_driver virtio_blk = {
 #endif
 };
 
-static int __init init(void)
+static int __init virtio_blk_init(void)
 {
 	int error;
 
@@ -1048,14 +1048,14 @@ static int __init init(void)
 	return error;
 }
 
-static void __exit fini(void)
+static void __exit virtio_blk_fini(void)
 {
 	unregister_virtio_driver(&virtio_blk);
 	unregister_blkdev(major, "virtblk");
 	destroy_workqueue(virtblk_wq);
 }
-module_init(init);
-module_exit(fini);
+module_init(virtio_blk_init);
+module_exit(virtio_blk_fini);
 
 MODULE_DEVICE_TABLE(virtio, id_table);
 MODULE_DESCRIPTION("Virtio block driver");