Use kmemdup() rather than duplicating its implementation.

By usign kmemdup() we can also get rid of the 'val' variable.

Detected with Coccinelle script.
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Reviewed-by: Horia Geantă <horia.geanta@nxp.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>