mem-ruby: MessageBuffer capacity check
mem-ruby: MessageBuffer capacity check

Trip assert if call enqueue on a full message buffer.

Change-Id: I842183d8bf2c681787f1b6ac23c95825095ad05d
Signed-off-by: Tiago Mück <02f879f33eea3aaf6781160757a59709a6f01bed@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/31254
Maintainer: Jason Lowe-Power <92de577f37050ad05b60626d2f17913f40dcb1a2@gmail.com>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Jason Lowe-Power <92de577f37050ad05b60626d2f17913f40dcb1a2@gmail.com>
Reviewed-by: Matthew Poremba <f1eb50f3368ce197c52b19f7fdb5aa7a278f15fd@amd.com>

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