crypto: ccp - Refactor out sev_fw_alloc()

Create a helper function sev_fw_alloc() which can be used to allocate
aligned memory regions for use by the PSP firmware. Currently only used
for the SEV-ES TMR region but will be used for the SEV_INIT_EX NV memory
region.

Signed-off-by: Peter Gonda <pgonda@google.com>
Reviewed-by: Marc Orr <marcorr@google.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Brijesh Singh <brijesh.singh@amd.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Marc Orr <marcorr@google.com>
Cc: Joerg Roedel <jroedel@suse.de>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: David Rientjes <rientjes@google.com>
Cc: John Allen <john.allen@amd.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>