Embedded System PRNG not seeding

I am working to get SSH running on a SPARC embedded system with a buildroot build of the 4.9.6 linux kernel. When I attempt to start the daemon or generate SSH keys I receive the message

# ssh-keygen
PRNG is not seeded

My /dev/random and /dev/urandom are in place

# ls -al /dev/*random*
crw-rw-rw-    1 root     root        1,   8 Jan  1 00:10 /dev/random
crw-rw-rw-    1 root     root        1,   9 Jan  1 00:10 /dev/urandom

And my entropy pool seems to be OK

# cat /proc/sys/kernel/random/entropy_avail 
825

Any thoughts on what I might be missing to get the PRNG seeded for SSH?