staging: wfx: fix coherency of hif_scan() prototype

staging: wfx: fix coherency of hif_scan() prototype

The function hif_scan() return the timeout for the completion of the
scan request. It is the only function from hif_tx.c that return another
thing than just an error code. This behavior is not coherent with the
rest of file. Worse, if value returned is positive, the caller can't
make say if it is a timeout or the value returned by the hardware.

Uniformize API with other HIF functions, only return the error code and
pass timeout with parameters.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200529121256.1045521-1-Jerome.Pouiller@silabs.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>