ts_31_102: TLV._tlv must point to the class, not an instance

In Change-Id I6d7c1bf49a8eaf3d8e50fb12888bf3d5b46b6c55 we fixed the
filesystem code to assume the self._tlv memper is a reference to a
class, and not an instance (as this is what the majority of the code
did).

However, it seems thre wer two instances where we actually had _tlv
reference an instance.  Change that to class so it's the same all over
the code base.

Change-Id: Ie4878ad6a92feafe47e375c4f5f3f198921e1e95
diff --git a/pySim/ts_31_102.py b/pySim/ts_31_102.py
index e2ab925..3ae88d3 100644
--- a/pySim/ts_31_102.py
+++ b/pySim/ts_31_102.py
@@ -335,7 +335,7 @@
     def __init__(self, fid="4f03", sfid=0x03, name='EF.5GS3GPPNSC', rec_len={57, None},
         desc='5GS 3GPP Access NAS Security Context'):
         super().__init__(fid, sfid=sfid, name=name, desc=desc, rec_len=rec_len)
-        self._tlv = EF_5GS3GPPNSC.FiveGSNasSecurityContext()
+        self._tlv = EF_5GS3GPPNSC.FiveGSNasSecurityContext
 
 # 3GPP TS 31.102 Section 4.4.11.6
 class EF_5GAUTHKEYS(TransparentEF):
@@ -351,7 +351,7 @@
     def __init__(self, fid='4f05', sfid=0x05, name='EF.5GAUTHKEYS', size={68, None},
             desc='5G authentication keys'):
         super().__init__(fid, sfid=sfid, name=name, desc=desc, size=size)
-        self._tlv = EF_5GAUTHKEYS.FiveGAuthKeys()
+        self._tlv = EF_5GAUTHKEYS.FiveGAuthKeys
 
 # 3GPP TS 31.102 Section 4.4.11.8
 class ProtSchemeIdList(BER_TLV_IE, tag=0xa0):