staging: r8712u: Fix Sparse warning in rtl871x_xmit.c

Sparse reports the following:
  CHECK   drivers/staging/rtl8712/rtl871x_xmit.c
drivers/staging/rtl8712/rtl871x_xmit.c:350:44: warning: restricted __le32 degrades to integer
drivers/staging/rtl8712/rtl871x_xmit.c:491:23: warning: incorrect type in initializer (different base types)
drivers/staging/rtl8712/rtl871x_xmit.c:491:23:    expected unsigned short [usertype] *fctrl
drivers/staging/rtl8712/rtl871x_xmit.c:491:23:    got restricted __le16 *<noident>
drivers/staging/rtl8712/rtl871x_xmit.c:580:36: warning: incorrect type in assignment (different base types)
drivers/staging/rtl8712/rtl871x_xmit.c:580:36:    expected unsigned short [unsigned] [short] [usertype] <noident>
drivers/staging/rtl8712/rtl871x_xmit.c:580:36:    got restricted __be16 [usertype] <noident>

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>