stats: Update some stats after simulated program exit behavior was changed.

The following CL delayed program exit and changed the stats for many if not
most of the SE mode regressions.

commit 2c1286865fc2542a0586ca4ff40b00765d17b348
Author: Brandon Potter <Brandon.Potter@amd.com>
Date: Wed Mar 1 14:52:23 2017 -0600

syscall-emul: Rewrite system call exit code

Change-Id: Id241f2b7d5374947597c715ee44febe1acc5ea16
Reviewed-on: https://gem5-review.googlesource.com/2656
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

stats: update references

tests: Recategorise regressions based on run time

This patch takes a first stab at recategorising the regression tests
based on actual run times. The simple-atomic and simple-timing runs of
vortex and twolf all finish in less than 180 s, and they are
consequently moved from long to quick. All realview64 linux-boot
regressions take more than 700 s, and they are therefore moved to
long.

Later patches will rename quick to short, and further divide the
regressions into short, medium and long.