radeon_replay/radeon_dp_aux: Use same DP_AUX defines as linux

This allows us to more easily integrate the code into linux.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
radeon_replay/radeon_dp_aux: Rename 'ack' field to 'reply'

This makes it more consistent with the naming in linux.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>