The Amlogic G12A has the hwrng module at the end of an unknown
"EFUSE" bus.

The hwrng is not enabled on the vendor G12A DTs, but is enabled on
next generation SM1 SoC family sharing the exact same memory mapping.

Let's add the "EFUSE" bus and the hwrng node.

This hwrng has been checked with the rng-tools rngtest FIPS tool :
rngtest: starting FIPS tests...
rngtest: bits received from input: 1630240032
rngtest: FIPS 140-2 successes: 81436
rngtest: FIPS 140-2 failures: 76
rngtest: FIPS 140-2(2001-10-10) Monobit: 10
rngtest: FIPS 140-2(2001-10-10) Poker: 6
rngtest: FIPS 140-2(2001-10-10) Runs: 26
rngtest: FIPS 140-2(2001-10-10) Long run: 34
rngtest: FIPS 140-2(2001-10-10) Continuous run: 0
rngtest: input channel speed: (min=3.784; avg=5687.521; max=19073.486)Mibits/s
rngtest: FIPS tests speed: (min=47.684; avg=52.348; max=52.835)Mibits/s
rngtest: Program run time: 30000987 microseconds
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>