gpu-compute: Fix LDS out-of-bounds behavior

gpu-compute: Fix LDS out-of-bounds behavior

The LDS is capable of handling out-of-bounds accesses,
that is, accesses that are outside the bounds of the
chunk allocated to a WG. Currently, the simulator asserts
on these accesses. This patch changes the behavior of the
LDS to return 0 for reads and dropping writes that are
out-of-bounds.

Change-Id: I5f467d0f52113e8565e1a3029e82fb89cc6f07ea
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/29940
Maintainer: Anthony Gutierrez <anthony.gutierrez@amd.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Matt Sinclair <mattdsinclair@gmail.com>