[sff8472.py] Make hex keys all lowercase (sonic-net#115)

Alpha chars in hex-based keys should be lowercase

Author: jleveque

sonic_platform_base/sonic_sfp/sff8472.py

@@ -281,7 +281,7 @@ class sff8472InterfaceId(sffbase):
              '09': 'MU',
              '0a': 'SG',
              '0b': 'Optical pigtail',
-             '0C': 'MPO Parallel Optic',
+             '0c': 'MPO Parallel Optic',
              '20': 'HSSDCII',
              '21': 'CopperPigtail',
              '22': 'RJ45'}