nouveau/headers: Add a MAX_BIT for structs

Reviewed-by: Mel Henning <mhenning@darkrefraction.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36995>

src/nouveau/headers/struct_parser.py

@@ -25,6 +25,7 @@ TEMPLATE_RS = Template("""\
 use std::ops::Range;
 
 % for s in structs:
+pub const ${s.name}_MAX_BIT: usize = ${s.max_bit};
     % for f in s.fields:
         % if f.stride:
 #[inline]
@@ -85,9 +86,11 @@ class Struct(object):
     def __init__(self, name):
         self.name = name
         self.fields = []
+        self.max_bit = 0
 
     def add_field(self, name, lo, hi, stride=0):
         self.fields.append(Field(name, lo, hi, stride))
+        self.max_bit = max(self.max_bit, hi)
 
 DRF_RE = re.compile(r'(?P<hi>[0-9]+):(?P<lo>[0-9]+)')
 FIELD_NAME_RE = re.compile(r'_?(?P<dw>[0-9]+)?_?(?P<name>.*)')