agx: Handle imadshl_agx, imsubshl_agx

Same hardware instructions as iadd/isub/imad/imsub, just with the extra input
represented in NIR as required.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22695>
1 file changed