virt/coco/sev-guest: Carve out the request issuing logic into a helper

virt/coco/sev-guest: Carve out the request issuing logic into a helper

commit 15d6638b90489d5e41819101d9cf31753c084b10 upstream.

This makes the code flow a lot easier to follow.

No functional changes.

  [ Tom: touchups. ]

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230307192449.24732-6-bp@alien8.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>