base: Add function to saturate SatCounter

Create a saturation function for the SatCounter that makes its
internal counter reach its maximum value.

Change-Id: Ibd30fa27c4ae2714dd48e3eba85addd035fb737c
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/20451
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

base: Add operators to SatCounter

Add shift, add and subtract assignment operators, as well as
copy and move constructor and assignments to SatCounter, so
that it they can be used by the prefetchers.

Also add extra useful functions to calculate saturation
oercentile so that the instantiator does not need to be aware
of the counter's maximum value.

Change-Id: I61d0cb28c8375b9d2774a39011e4a0aa6fe9ccb7
Signed-off-by: Daniel <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17996
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>

base: Add GTest to SatCounter

Add a GTest to the SatCounter class.

Change-Id: Iaf1b18db9fe8d7fe32e0e40c7947dcd1fd6cc33b
Signed-off-by: Daniel <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17994
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>