sched/pelt: Fix task util_est update filtering

Being called for each dequeue, util_est reduces the number of its updates
by filtering out when the EWMA signal is different from the task util_avg
by less than 1%. It is a problem for a sudden util_avg ramp-up. Due to the
decay from a previous high util_avg, EWMA might now be close enough from
the new util_avg. No update would then take place while it would leave
ue.enqueued with an out-of-date value.

Taking into account the two util_est members, EWMA and enqueued for the
filtering, ensures, for both, an up-to-date value.

This problem has been observed using LISA's UtilConvergence:test_means on
the sd845c board.

Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>