arch-gcn3: convert vALU instruction counters from 32 to 64-bit

arch-gcn3: convert vALU instruction counters from 32 to 64-bit

The vALU instruction counters were previously 32 bits, but for some
workloads this value wraps around and triggers an assert failure
because the max vALU operations are reached.  To resolve this, this
commit increases the counter size to 64 bits.

Change-Id: I90ed4514669485cfea7ccc37ba9d69665277bccb
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/29950
Maintainer: Anthony Gutierrez <anthony.gutierrez@amd.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Matt Sinclair <mattdsinclair@gmail.com>