libblock: Return RTEMS_NO_MEMORY on allocation failure

In rtems_bdpart_register(), when create_logical_disk_name() fails to
allocate memory and returns NULL, the error code variable 'esc' was
incorrectly assigned 'sc' (which evaluates to RTEMS_SUCCESSFUL).

This caused the function to falsely return RTEMS_SUCCESSFUL even when
memory allocation failed. Fix it by assigning RTEMS_NO_MEMORY.

cpukit/libblock/src/bdpart-register.c

@@ -105,7 +105,7 @@ rtems_status_code rtems_bdpart_register(
     &logical_disk_marker
   );
   if ( logical_disk_name == NULL ) {
-    esc = sc;
+    esc = RTEMS_NO_MEMORY;
     goto cleanup;
   }