sched/cputime, proc/stat: Fix incorrect guest nice cpustat value

The value being used for guest_nice should be CPUTIME_GUEST_NICE
and not CPUTIME_USER.

Fixes: 26dae145 ("procfs: Use all-in-one vtime aware kcpustat accessor")
Signed-off-by: Flavio Leitner <fbl@sysclose.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20191205020344.14940-1-frederic@kernel.org


Signed-off-by: Ingo Molnar <mingo@kernel.org>