arch-power: Refactor argument registers

This reintroduces the argument register constants that
were removed in commit 7bb456f02 ("arch-power: Delete
unused register related constants"), adds a definition
for the sixth argument register and switches to these
constants to specify the arguments used by the system
call ABI.

Change-Id: I5804f4d2b27a04d0e7b69132e5abce5761b239f5
Signed-off-by: Sandipan Das <sandipan@linux.ibm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/40938
Reviewed-by: Boris Shingarov <shingarov@labware.com>
Maintainer: Boris Shingarov <shingarov@labware.com>
Tested-by: kokoro <noreply+kokoro@google.com>
2 files changed