staging: rtl8192e: Use kmemdup for duplicating memory

Instead of allocating memory (kmalloc) and copying (memcpy)
from source, memory can be duplicated using kmemdup

Signed-off-by: Hema Prathaban <hemaklnce@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>