powerpc/vdso: Prepare introduction of struct vdso_clock

To support multiple PTP clocks, the VDSO data structure needs to be
reworked. All clock specific data will end up in struct vdso_clock and in
struct vdso_time_data there will be array of VDSO clocks. At the moment,
vdso_clock is simply a define which maps vdso_clock to vdso_time_data.

To prepare for the rework of the data structures, replace the struct
vdso_time_data pointer with a struct vdso_clock pointer where applicable.

No functional change.

Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250303-vdso-clock-v1-17-c1b5c69a166f@linutronix.de

arch/powerpc/include/asm/vdso/gettimeofday.h

@@ -99,7 +99,7 @@ static __always_inline u64 __arch_get_hw_counter(s32 clock_mode,
 	return get_tb();
 }
 
-static inline bool vdso_clocksource_ok(const struct vdso_time_data *vd)
+static inline bool vdso_clocksource_ok(const struct vdso_clock *vc)
 {
 	return true;
 }