fix for:
drivers/staging/rtl8192su/r8192U_core.c: In function ‘rtl8192SU_MacConfigAfterFwDownload’:
drivers/staging/rtl8192su/r8192U_core.c:4403:24: warning: comparison between ‘rtl819xUsb_loopback_e’ and ‘enum _RTL8192SUSB_LOOPBACK’
drivers/staging/rtl8192su/r8192U_core.c:4405:30: warning: comparison between ‘rtl819xUsb_loopback_e’ and ‘enum _RTL8192SUSB_LOOPBACK’