python: Better iterate over dictionaries

In Python 2, dictionaries have 2 sets of methods to iterate over their
keys and values: keys()/values()/items() and iterkeys()/itervalues()/iteritems().

The former return lists while the latter return iterators.

Python 3 dropped the method which return lists, and renamed the methods
returning iterators to keys()/values()/items().

Using those names makes the scripts compatible with both Python 2 and 3.

Signed-off-by: Mathieu Bridon <bochecha@daitauha.fr>
Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>

src/compiler/nir/nir_opcodes_c.py

@@ -116,7 +116,7 @@ nir_type_conversion_op(nir_alu_type src, nir_alu_type dst, nir_rounding_mode rnd
 }
 
 const nir_op_info nir_op_infos[nir_num_opcodes] = {
-% for name, opcode in sorted(opcodes.iteritems()):
+% for name, opcode in sorted(opcodes.items()):
 {
    .name = "${name}",
    .num_inputs = ${opcode.num_inputs},