staging: wfx: fix firmware location

There is currently, a mismatch between the location of the firmware in
linux-firmware and the path written in the driver.

We take this opportunity to relocate the WF200 firmware in wfx/ instead
of silabs/.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20220113085524.1110708-29-Jerome.Pouiller@silabs.com


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