vTPM : fix arm issue by selecting correct dev name based on arch

The vTPM device name is different on ARM and x86. This patch fixes the
the issue by selecting the correct device name based on the architecture.

Signed-off-by: Shahriyar Jalayeri <shahriyar@zededa.com>

pkg/pillar/hypervisor/kvm.go

@@ -426,7 +426,14 @@ const qemuSwtpmTemplate = `
   chardev = "swtpm"
 
 [device "tpm-tis"]
+# 'virt' refers to aarch64
+# 'tpm-tis-device' for aarch64 versus 'tpm-tis' for x86
+# Reference: https://listman.redhat.com/archives/libvir-list/2021-February/msg00647.html
+{{- if eq .Machine "virt"}}
+  driver = "tpm-tis-device"
+{{- else}}
   driver = "tpm-tis"
+{{- end}}
   tpmdev = "tpm0"
 `