staging: wfx: fix race between configure_filter and remove_interface

staging: wfx: fix race between configure_filter and remove_interface

wfx_remove_interface() and wfx_configure_filter() can be run
concurrently. Therefore, this patch protect access to the list of
interfaces from wfx_configure_filter().

Notice that wfx_configure_filter() now lock "conf_lock" and "scan_lock".
Beside that, wfx_hw_scan_work() also access to the same locks. So we
have to lock them in same order to avoid any deadlock.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200410133239.438347-2-Jerome.Pouiller@silabs.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>