This enables Random Number Generator support on Northstar (described in
DT with brcm,bcm5301x-rng).
It's also a workaround for OpenWrt bug with kernel config causing:
Broadcom BCM2835/BCM63xx Random Number Generator support (HW_RANDOM_BCM2835) [Y/n/m/?] (NEW)
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>