x86, microcode, AMD: Add a vendor-specific exit function

This will be used to do cleanup work before the driver exits.

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
diff --git a/arch/x86/kernel/microcode_amd.c b/arch/x86/kernel/microcode_amd.c
index d494799..e8a68c2 100644
--- a/arch/x86/kernel/microcode_amd.c
+++ b/arch/x86/kernel/microcode_amd.c
@@ -353,3 +353,7 @@
 {
 	return &microcode_amd_ops;
 }
+
+void __exit exit_amd_microcode(void)
+{
+}