wl12xx: fix some endianess bugs

pointed out by sparse warnings:

  CHECK   drivers/net/wireless/wl12xx/cmd.c
drivers/net/wireless/wl12xx/cmd.c:987:20: warning: incorrect type in assignment (different base types)
drivers/net/wireless/wl12xx/cmd.c:987:20:    expected restricted __le16 [usertype] aging_period
drivers/net/wireless/wl12xx/cmd.c:987:20:    got int
  CHECK   drivers/net/wireless/wl12xx/tx.c
drivers/net/wireless/wl12xx/tx.c:197:2: warning: cast from restricted __le16
drivers/net/wireless/wl12xx/tx.c:197:2: warning: cast from restricted __le16
drivers/net/wireless/wl12xx/tx.c:197:2: warning: cast from restricted __le16
  CHECK   drivers/net/wireless/wl12xx/acx.c
drivers/net/wireless/wl12xx/acx.c:816:23: warning: incorrect type in assignment (different base types)
drivers/net/wireless/wl12xx/acx.c:816:23:    expected restricted __le32 [usertype] rate_policy_idx
drivers/net/wireless/wl12xx/acx.c:816:23:    got unsigned char [unsigned] [usertype] idx

Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>