hw_random: timeriomem_rng: update to support more than one device

timeriomem_rng only supports a single device instance.  This patch
enables multiple timeriomem_rng devices to coexist as well as adds
some additional error checking.

Signed-off-by: Alexander Clouter <alex@digriz.org.uk>
hw_random: timeriomem_rng: added devicetree hooks

This patch allows timeriomem_rng to be used via devicetree.

Signed-off-by: Alexander Clouter <alex@digriz.org.uk>
arm: orion5x: add DT support for HWRNG on the TS-7800

Plumb in support for the HWRNG on the DT platform TS-7800.

Signed-off-by: Alexander Clouter <alex@digriz.org.uk>