hwrng: bcm2835 - Add support for Broadcom BCM5301x

The Broadcom BCM5301x SoCs (Northstar) utilize the same random number
generator peripheral as Northstar Plus and BCM2835, but just like the
NSP SoC, we need to enable the interrupt.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>