asahi: Strip ? in GenXML

Sometimes it's nice to have boolean flags with ? in the name, allow this by
stripping ? when generating the sanitized C name.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23998>

src/asahi/lib/gen_pack.py

@@ -143,6 +143,7 @@ def to_alphanum(name):
         '"': '',
         '+': '',
         '\'': '',
+        '?': '',
     }
 
     for i, j in substitutions.items():