staging: wilc1000: use kmemdup instead of kmalloc in add_network_to_shadow()

Use kmemdup instead of kmalloc & memcpy in add_network_to_shadow(). Also
added  code to set 'ies_len' to zero in case of memory allocation
failure.

Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>