perf/x86/64: Report regs_user->ax too in get_regs_user()

I don't see why we report e.g. orix_ax, which is not always
meaningful, but don't report ax, which is meaningful.

Signed-off-by: Denys Vlasenko <[e-mail]>
Cc: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

arch/x86/kernel/perf_regs.c

···
 	 * On 32-bit entry points, they are saved too except r8..r11.
 	 */
 	regs_user_copy->ip = user_regs->ip;
+	regs_user_copy->ax = user_regs->ax;
 	regs_user_copy->cx = user_regs->cx;
 	regs_user_copy->dx = user_regs->dx;
 	regs_user_copy->si = user_regs->si;