get_device, put_device and device_release_driver are no longer available to non-GPL modules.
The whole process of unregistering the device from another driver seems dodgy, lets just skip it

--- slmodem-2.9.10/drivers/amrmo_init.c.orig	2005-01-03 14:52:23.178287912 +0000
+++ slmodem-2.9.10/drivers/amrmo_init.c	2005-01-03 15:06:46.603027400 +0000
@@ -718,15 +718,8 @@
 				dev->driver->remove(dev);
 			dev->driver = NULL;
 #else
-			struct device *reldev = get_device(&dev->dev);
-			AMRMO_DBG("device %04x:%04x is grabbed by driver %s: try to release\n",
-				  dev->vendor,dev->device,
-				  (reldev&&reldev->driver)?
-				   reldev->driver->name:"unknown");
-			if (reldev) {
-				device_release_driver(reldev);
-				put_device(reldev);
-			}
+			AMRMO_DBG("device %04x:%04x is grabbed by another driver, ignoring",
+				  dev->vendor,dev->device);
 #endif
 		}
 	}