x86/sev: Drop unnecessary parameter in snp_issue_guest_request()

Commit

  3e385c0d ("virt: sev-guest: Move SNP Guest Request data pages handling under snp_cmd_mutex")

moved @input from snp_msg_desc to snp_guest_req which is passed to
snp_issue_guest_request().

Drop the extra parameter.

No functional change intended.

Signed-off-by: Alexey Kardashevskiy <aik@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Dionna Glaze <dionnaglaze@google.com>
Link: https://lore.kernel.org/20250611040842.2667262-5-aik@amd.com