rtl8192du: Remove MAC_ADDR_LEN and use ETH_ALEN instead

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
rtl8192du: Remove SUCCESS and FAIL

These two macros are not used. In addition, their definitions
conflict with _SUCCESS and _FAIL.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
rtl8192du: Remove macros _SUCCESS and _FAIL

These are set to 1 and 0 respectively.

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