freedreno/registers: remove python 3.9 dependency for compiling msm

Synced from kernel commit bb1953588068 ("drm/msm: remove python 3.9
dependency for compiling msm").

Since commit 5acf49119630 ("drm/msm: import gen_header.py script from Mesa"),
compilation is broken on machines having python versions older than 3.9
due to dependency on argparse.BooleanOptionalAction.

Switch to use simple bool for the validate flag to remove the dependency.

Signed-off-by: Rob Clark <rob.clark@oss.qualcomm.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/37216>

src/freedreno/registers/gen_header.py

@@ -567,7 +567,7 @@ class Parser(object):
 		self.variants.add(reg.domain)
 
 	def do_validate(self, schemafile):
-		if self.validate == False:
+		if not self.validate:
 			return
 
 		try:
@@ -972,7 +972,8 @@ def main():
 	parser = argparse.ArgumentParser()
 	parser.add_argument('--rnn', type=str, required=True)
 	parser.add_argument('--xml', type=str, required=True)
-	parser.add_argument('--validate', action=argparse.BooleanOptionalAction)
+	parser.add_argument('--validate', default=False, action='store_true')
+	parser.add_argument('--no-validate', dest='validate', action='store_false')
 
 	subparsers = parser.add_subparsers()
 	subparsers.required = True