afs: Fix the fallback handling for the YFS.RemoveFile2 RPC call

Fix a pair of bugs in the fallback handling for the YFS.RemoveFile2 RPC
call:

 (1) Fix the abort code check to also look for RXGEN_OPCODE.  The lack of
     this masks the second bug.

 (2) call->server is now not used for ordinary filesystem RPC calls that
     have an operation descriptor.  Fix to use call->op->server instead.

Fixes: e49c7b2 ("afs: Build an abstraction around an "operation" concept")
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/109541.1736865963@warthog.procyon.org.uk
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: dhowells

fs/afs/yfsclient.c

@@ -666,8 +666,9 @@ static int yfs_deliver_fs_remove_file2(struct afs_call *call)
 static void yfs_done_fs_remove_file2(struct afs_call *call)
 {
 	if (call->error == -ECONNABORTED &&
-	    call->abort_code == RX_INVALID_OPERATION) {
-		set_bit(AFS_SERVER_FL_NO_RM2, &call->server->flags);
+	    (call->abort_code == RX_INVALID_OPERATION ||
+	     call->abort_code == RXGEN_OPCODE)) {
+		set_bit(AFS_SERVER_FL_NO_RM2, &call->op->server->flags);
 		call->op->flags |= AFS_OPERATION_DOWNGRADE;
 	}
 }