net: wl12xx: do not use kfree'd memory

wl1271_dump() uses cmd after kfree(cmd). Move kfree() just after
wl1271_dump().

Signed-off-by: Kulikov Vasiliy <segooon@gmail.com>
Acked-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>