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

[ Upstream commit e30458d690f35abb01de8b3cbc09285deb725d00 ]

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: e49c7b2f ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>