ARM: dts: imx51: Add sahara crypto support

The sahara crypto block on i.MX51 has the same IP version as
the one on i.MX53.

Add support for it.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>