rng: Add StarFive JH7110 RNG driver

Adds to support JH7110 TRNG driver which is based on linux kernel's
jh7110-trng.c. This can support to generate 256-bit random numbers and
128-bit but this makes 256-bit default for convenience.

Signed-off-by: Chanho Park <chanho61.park@samsung.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>