staging: wfx: drop useless update of macaddr

Mac address is set in wfx_add_interface() and removed in
wfx_remove_interface().

Currently, there is also an additional update of mac address in
wfx_do_unjoin(). It has no rationale. Mac address is already present
and nothing has changed it. Therefore, we can drop it.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200410133239.438347-20-Jerome.Pouiller@silabs.com


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