crypto: caam - Fix job ring discovery in controller driver

The SEC Controller driver creates platform devices for it's child job ring nodes.
Currently the driver uses for_each_compatible routine which traverses
the whole device tree to create the job rings for the platform device.
The patch changes this to search for the compatible property of job ring
only in the child nodes i.e., the job rings are created as per the number
of children associated with the crypto node.

Signed-off-by: Nitesh Lal <NiteshNarayanLal@freescale.com>
Reviewed-by: Horia Geanta <horia.geanta@freescale.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>