staging: wfx: fix double free

In case of error in wfx_probe(), wdev->hw is freed. Since an error
occurred, wfx_free_common() is called, then wdev->hw is freed again.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Reviewed-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Fixes: 4033714d ("staging: wfx: fix init/remove vs IRQ race")
Link: https://lore.kernel.org/r/20200505123757.39506-4-Jerome.Pouiller@silabs.com


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