USB: utilize round_jiffies_up_relative()

This patch (as1178) uses the new round_jiffies_up_relative() routine
for setting the autosuspend delayed_work timer.  It's appropriate
since we don't care too much about the exact length of the delay, but
we don't want it to be too short (rounded down).

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>