freedreno/registers: Fix gen_header.py for older python3 versions

The gen_header.py script is failing for older versions of python3 such
as python 3.5. Two issues observed with python 3.5 are ...

 1. Python 3 versions prior to 3.6 do not support the f-string format.
 2. Early python 3 versions do not support the 'required' argument for
    the argparse add_subparsers().

Fix both of the above so that older versions of python 3 still work.

Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28780>

src/freedreno/registers/gen_header.py

@@ -322,7 +322,7 @@ class Array(object):
 			indices = []
 		if self.length != 1:
 			if self.fixed_offsets:
-				indices.append((self.index_ctype(), None, f"__offset_{self.local_name}"))
+				indices.append((self.index_ctype(), None, "__offset_%s" % self.local_name))
 			else:
 				indices.append((self.index_ctype(), self.stride, None))
 		return indices
@@ -962,7 +962,8 @@ def main():
 	parser.add_argument('--xml', type=str, required=True)
 	parser.add_argument('--validate', action=argparse.BooleanOptionalAction)
 
-	subparsers = parser.add_subparsers(required=True)
+	subparsers = parser.add_subparsers()
+	subparsers.required = True
 
 	parser_c_defines = subparsers.add_parser('c-defines')
 	parser_c_defines.set_defaults(func=dump_c_defines)