freedreno/computerator: fix missing dependency on generated header

freedreno/computerator: fix missing dependency on generated header

Fixes:
```
 ../mesa-freedreno-20.2.0_pre/src/freedreno/computerator/ir3_asm.c:25:10: fatal error: 'ir3/ir3_parser.h' file not found
 #include "ir3/ir3_parser.h"
          ^~~~~~~~~~~~~~~~~~
 1 error generated.
```

Fixes: da467817e3e ("freedreno/ir3: Move ir3 assembler to backend compiler")
Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Eric Engestrom <eric@engestrom.ch>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5340>