[NET_SCHED]: Export real timer resolution in /proc/net/psched

The timer resolution exported in /proc/net/psched is used by userspace to
calculate HTB's burst values. Currently it is set to HZ, since we're now
using hrtimers, use KTIME_MONOTONIC_RES, which makes HTB use smaller burst
values.

This patch also affects libnl, which incorrectly uses this value for
the SFQ perturbation parameter, which is always in seconds, and some
routing cache values, which are in USER_HZ, so both cases are broken
anyway.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>