staging: wfx: simplify the check if the the device is associated

Firmware dislikes the driver enables PS when it is not yet associated.
The current check for that condition is more complex than necessary.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200420160311.57323-2-Jerome.Pouiller@silabs.com


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