arm/arm64: arch_timer: Use archdata to indicate vdso suitability

Instead of comparing the name to a magic string, use archdata to
explicitly communicate whether the arch timer is suitable for
direct vdso access.

Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Russell King <rmk+kernel@armlinux.org.uk>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Scott Wood <oss@buserror.net>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/include/asm/clocksource.h

@@ -0,0 +1,8 @@
+#ifndef _ASM_CLOCKSOURCE_H
+#define _ASM_CLOCKSOURCE_H
+
+struct arch_clocksource_data {
+	bool vdso_direct;	/* Usable for direct VDSO access? */
+};
+
+#endif