Fix subtype in PartitionTable.find_by_type

Fix ptype->subtype

Closes https://github.com/espressif/esp-idf/pull/4723

components/partition_table/gen_esp32part.py

@@ -160,7 +160,7 @@ class PartitionTable(list):
             subtype = SUBTYPES[int(ptype)][subtype]
         except KeyError:
             try:
-                ptype = int(ptype, 0)
+                subtype = int(subtype, 0)
             except TypeError:
                 pass