staging: wilc1000: fix infinite loop and out-of-bounds access

If i < slot_id is initially true then it will remain true. Also,
as i is being decremented it will end up accessing memory out of
bounds.

Fix this by incrementing *i* instead of decrementing it.

Addresses-Coverity-ID: 1468454 ("Infinite loop")
Fixes: faa65764 ("staging: wilc1000: refactor scan() to free kmalloc memory on failure cases")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: Ajay Singh <ajay.kathat@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>