base: Rename Flags::update as Flags::replace

base: Rename Flags::update as Flags::replace

The function name `update` is too generic. Given that
the expected functionality is to replace the selected
flag bits with the bits provided as parameters, rename
it as `replace`.

Change-Id: Ic7613ae09ecf9b92e31103b4e928192c07e9b640
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/38737
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>