build: Consolidate sev_snp feature usage

Since igvm is a required feature of sev_snp and also sev_snp is x86-64
only the cfg attributes at build time can be consolidated & simplified.

Signed-off-by: Rob Bradford <rbradford@meta.com>

vmm/src/lib.rs

@@ -89,12 +89,7 @@ pub mod migration_transport;
 mod pci_segment;
 pub mod seccomp_filters;
 mod serial_manager;
-#[cfg(all(
-    feature = "kvm",
-    feature = "sev_snp",
-    feature = "fw_cfg",
-    target_arch = "x86_64"
-))]
+#[cfg(all(feature = "kvm", feature = "sev_snp", feature = "fw_cfg"))]
 pub(crate) mod sev;
 mod sigwinch_listener;
 mod sync_utils;