staging: r8188eu: os_dep: use kmemdup instead of kzalloc and memcpy

Fixes coccicheck warning:WARNING opportunity for kmemdup in ioctl_linux.c

Acked-by: Phillip Potter <phil@philpotter.co.uk>
Signed-off-by: Saurav Girepunje <saurav.girepunje@gmail.com>
Link: https://lore.kernel.org/r/YTJhwQstKPUYRwN+@user


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>