Staging: rtl8192u: fix a reversed test

Sean MacLennan fixed this in the rtl8192e driver and we should fix
it here as well.

It's pretty harmless.  This information comes from the firmware, if
we were to hit this bug we would read beyond the end of the array
once or twice before returning and update our statistics with bogus
data.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>