Add support for matching one of several different units in toNum. The units parameter can now either be a tuple or a string describing the supported unit(s). The function now returns a (magnitude, unit) tuple. Change-Id: I683819722a93ade91a6def2bfa77209c29b4b39e Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/39217 Tested-by: kokoro <noreply+kokoro@google.com> Reviewed-by: Gabe Black <gabe.black@gmail.com> Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>