mem: Mark MemObject as deprecated.

mem: Mark MemObject as deprecated.

It's constructor will now warn that it's deprecated and suggest using
ClockedObject directly. This change also gets rid of the params()
method and the Params typedef since they are functionally equivalent to
the ClockedObject versions.

It also removes the include of mem/port.hh which is not used in
mem_object.hh. This may break code which purposefully or (more likely)
accidentally depended on that transitive include from mem_object.hh.

Change-Id: I6dab3ba626e3f3ab6a6bd86edcf4f5cb4d6d2c45
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/20720
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>