wl12xx: fix testmode test/interrogate commands

fix several issues in testmode test/interrogate commands:
1. check the driver state is not OFF.
2. wakeup the chip from elp (if needed)
3. fix memory leak in wl1271_tm_cmd_interrogate()

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