The only PSP mailbox that currently supports interrupt on completion
is the SEV mailbox.  Drop the dead code for the TEE subdriver to
potentially call it.
Acked-by: Rijo Thomas <Rijo-john.Thomas@amd.com>
Acked-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>