virt/coco/sev-guest: Remove the disable_vmpck label in handle_guest_request()

Call the function directly instead.

No functional changes.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20230307192449.24732-5-bp@alien8.de