rtl8188eu: Fix smatch warnings in core/rtw_security.c

Smatch shows the following:
  CHECK   /home/finger/rtl8188eu/core/rtw_security.c
/home/finger/rtl8188eu/core/rtw_security.c:2077 rijndaelKeySetupEnc() warn: '4' 4 can't fit into 4611686018427387903 'rk'
/home/finger/rtl8188eu/core/rtw_security.c:2108 rijndaelEncrypt() warn: '8' 8 can't fit into 4611686018427387903 'rk'

These warnings were fixed by removing a number of unused routines.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
rtl8188eu: Add support for DLINK DWA-125 REV D1

User sergforce reported this on the GitHub issues list.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>