uapi: v4l2_ext_control struct must be specifically packed

Looks like the v4l2_ext_control struct must be packed with an alignment
of 1 byte.

Signed-off-by: Sylvain Petinot <[email protected]>

v4l2/uapi/v4l2.py

@@ -3613,6 +3613,7 @@ class struct_v4l2_ext_control(Structure):
     'reserved2',
     'unnamed_1',
 ]
+struct_v4l2_ext_control._pack_ = 1
 struct_v4l2_ext_control._anonymous_ = [
     'unnamed_1',
 ]