y2038: vdso: powerpc: avoid timespec references

As a preparation to stop using 'struct timespec' in the kernel,
change the powerpc vdso implementation:

- split up the vdso data definition to have equivalent members
   for seconds and nanoseconds instead of an xtime structure

- use timespec64 as an intermediate for the xtime update

- change the asm-offsets definition to be based the appropriate
  fixed-length types

This is only a temporary fix for changing the types, in order
to actually support a 64-bit safe vdso32 version of clock_gettime(),
the entire powerpc vdso should be replaced with the generic
lib/vdso/ implementation. If that happens first, this patch
becomes obsolete.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/powerpc/kernel/time.c

@@ -885,7 +885,7 @@ static notrace u64 timebase_read(struct clocksource *cs)
 
 void update_vsyscall(struct timekeeper *tk)
 {
-	struct timespec xt;
+	struct timespec64 xt;
 	struct clocksource *clock = tk->tkr_mono.clock;
 	u32 mult = tk->tkr_mono.mult;
 	u32 shift = tk->tkr_mono.shift;
@@ -957,7 +957,8 @@ void update_vsyscall(struct timekeeper *tk)
 	vdso_data->tb_to_xs = new_tb_to_xs;
 	vdso_data->wtom_clock_sec = tk->wall_to_monotonic.tv_sec;
 	vdso_data->wtom_clock_nsec = tk->wall_to_monotonic.tv_nsec;
-	vdso_data->stamp_xtime = xt;
+	vdso_data->stamp_xtime_sec = xt.tv_sec;
+	vdso_data->stamp_xtime_nsec = xt.tv_nsec;
 	vdso_data->stamp_sec_fraction = frac_sec;
 	smp_wmb();
 	++(vdso_data->tb_update_count);