arch-vega: Implement ds_read_i8

Read one byte with sign extended from LDS.

Change-Id: I9cb9b4033c6f834241cba944bc7e6a7ebc5401be
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/67076
Maintainer: Matt Sinclair <mattdsinclair@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Matt Sinclair <mattdsinclair@gmail.com>
2 files changed