gpu-compute, mem-ruby, configs: Add GCN3 ISA support to GPU model

Change-Id: Ibe46970f3ba25d62ca2ade5cbc2054ad746b2254
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/29912
Reviewed-by: Anthony Gutierrez <anthony.gutierrez@amd.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Anthony Gutierrez <anthony.gutierrez@amd.com>
Tested-by: kokoro <noreply+kokoro@google.com>
86 files changed