radv: Separate option to print shader disassembly.

Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Konstantin Seurer <konstantin.seurer@gmail.com>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Acked-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/32079>

docs/envvars.rst

@@ -1434,6 +1434,8 @@ RADV driver environment variables
       Dump compute (and ray tracing) shaders.
    ``nir``
       Dump NIR for selected shader stages.
+   ``asm``
+      Dump shader disassembly for selected shader stages.
 
 .. envvar:: RADV_FORCE_FAMILY