x86/apic: Add support to send NMI IPI for Secure AVIC

x86/apic: Add support to send NMI IPI for Secure AVIC

Secure AVIC introduces a new field in the APIC backing page "NmiReq" that has
to be set by the guest to request a NMI IPI through APIC_ICR write.

Add support to set NmiReq appropriately to send NMI IPI.

Co-developed-by: Kishon Vijay Abraham I <kvijayab@amd.com>
Signed-off-by: Kishon Vijay Abraham I <kvijayab@amd.com>
Signed-off-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tianyu Lan <tiala@microsoft.com>
Link: https://lore.kernel.org/20250828111213.208933-1-Neeraj.Upadhyay@amd.com