staging: wilc1000: fix incorrect copy of pmkid data

The pmkid data is meant be be copied to the previous item in the
pmkidlist, however the code is just copying the data to itself because
the src index into pmkidlist is the same as the dst index into pmkidlist.
Fix this with i + 1 instead of i.

Detected by CoverityScan,CID#13339465 ("Overlapping buffer in memory copy")

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>