powerpc/fsl: Add property for 'era' in SEC dts crypto node

The crypto node now contains a new property 'fsl,sec-era'.
This is required so that applications can retrieve era info without
having to be able to read SEC's register space.

Signed-off-by: Vakul Garg <vakul@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>