arm64: Add build salt to the vDSO

The vDSO needs to have a unique build id in a similar manner
to the kernel and modules. Use the build salt macro.
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

arch/arm64/kernel/vdso/note.S

@@ -22,7 +22,10 @@
 #include <linux/uts.h>
 #include <linux/version.h>
 #include <linux/elfnote.h>
+#include <linux/build-salt.h>
 
 ELFNOTE_START(Linux, 0, "a")
 	.long LINUX_VERSION_CODE
 ELFNOTE_END
+
+BUILD_SALT