ts_102_221: The BTLV IEs FILE SIZE and TOTAL FILE SIZE have a min length

The TLV IEs FILE SIZE and TOTAL FILE SIZE have a minimum length of 2
byte. Even when the length is in the single digit range two bytes must
be used. See also: ETSI TS 102 221, section 11.1.1.4.1 and 11.1.1.4.2

Change-Id: Ief113ce8fe3bcae2c9fb2ff4138df9ccf98d26ff
diff --git a/pySim/ts_102_221.py b/pySim/ts_102_221.py
index e7aff97..08e836c 100644
--- a/pySim/ts_102_221.py
+++ b/pySim/ts_102_221.py
@@ -80,11 +80,11 @@
 
 # ETSI TS 102 221 11.1.1.4.2
 class FileSize(BER_TLV_IE, tag=0x80):
-    _construct = GreedyInteger()
+    _construct = GreedyInteger(minlen=2)
 
 # ETSI TS 102 221 11.1.1.4.2
 class TotalFileSize(BER_TLV_IE, tag=0x81):
-    _construct = GreedyInteger()
+    _construct = GreedyInteger(minlen=2)
 
 # ETSI TS 102 221 11.1.1.4.3
 class FileDescriptor(BER_TLV_IE, tag=0x82):