wlcore: remove recover cmd from testmode

This command is buggy (doesn't take the mutex) and unused. Instead, the
"start_recovery" file is used for the same purpose. Remove the code but
keep the command constant to avoid breaking the testmode ABI.

Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>