staging: wilc1000: replace kmalloc/memcpy with kmemdup

This patch replaces kmalloc followed by memcpy with kmemdup.
It is also added error checking of kmemdup.

Signed-off-by: Chaehyun Lim <chaehyun.lim@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>