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.

Fixes: 5acf49119630 ("drm/msm: import gen_header.py script from Mesa")
Signed-off-by: Abhinav Kumar <[e-mail]>
Tested-by: Douglas Anderson <[e-mail]>
Reviewed-by: Dmitry Baryshkov <[e-mail]>
Signed-off-by: Thierry Reding <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/msm/registers/gen_header.py

···
 		self.variants.add(reg.domain)
 
 	def do_validate(self, schemafile):
-		if self.validate == False:
+		if not self.validate:
 			return
 
 		try:
···
 	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