wlags49_h2: Fix overflow in wireless_set_essid()

This patch prevents the wireless_set_essid() function from overwriting
the last byte of the NetworkName buffer which must be NULL.

Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>