staging: wfx: use more power-efficient sleep for reset

Replace udelay() with usleep_range() as all uses are in a sleepable context.

Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Link: https://lore.kernel.org/r/59e1e4e5bd80c1879ef36eaa59916e47005dbb04.1581416843.git.mirq-linux@rere.qmqm.pl


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