dev-hsa: Properly mask HSA packet header bits

The HSA packet macros were not actually masking the header bits
properly. Add a mask call around the width (number of bits) of the field
being masked.

Change-Id: Ia5e5fb0451296e99a85fb12a5f73b27aea72fc2e
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/57669
Reviewed-by: Matt Sinclair <mattdsinclair@gmail.com>
Maintainer: Matt Sinclair <mattdsinclair@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
1 file changed