staging: wfx: disabling keep alive during unjoin is useless

After a call to hif_reset(), the parameters associated with BSS are
reset. So, it useless to explicitly reset the keep alive period.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200410133239.438347-10-Jerome.Pouiller@silabs.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>