mem-cache: Move Target to QueueEntry

WriteQueueEntry's target has 100% functionality overlap with MSHR's,
therefore make it base to MSHR::Target.

Change-Id: I48614e78179d708bd91bbe75a752e5a05146e8eb
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17534
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
6 files changed