mem-ruby, gpu-compute: update TCP_latency comment

Update the TCP_latency input arg to reflect what it does -- in
combination with the number of banks, it determines the number of
accesses that can happen in the L1 (TCP) in a given cycle.  It does
not directly affect the L1 latency as the name implies.  Instead,
the mandatory_queue_latency does this.

Change-Id: Ib6cbc8367ce2b1f30005d137384f53650a403b49
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/61309
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Matthew Poremba <matthew.poremba@amd.com>

configs/ruby/GPU_VIPER.py

@@ -373,7 +373,9 @@ def define_options(parser):
     parser.add_argument("--WB_L2", action="store_true", default=False,
                         help="writeback L2")
     parser.add_argument("--TCP_latency", type=int, default=4,
-                        help="TCP latency")
+                        help="In combination with the number of banks for the "
+                        "TCP, this determines how many requests can happen "
+                        "per cycle (i.e., the bandwidth)")
     parser.add_argument("--TCC_latency", type=int, default=16,
                         help="TCC latency")
     parser.add_argument("--tcc-size", type=str, default='256kB',