Add a driver for the rp2350 hardware true random number generator.
Enabling CONFIG_RP23XX_RNG selects ARCH_HAVE_RNG and builds the driver,
which registers /dev/random (and /dev/urandom when CONFIG_DEV_URANDOM
selects the architecture source, DEV_URANDOM_ARCH). Each read enables
the entropy source, waits for a valid 192-bit entropy holding register
(EHR) sample, reads the six 32-bit EHR words, and repeats until the
request is satisfied.
Document the TRNG on the rp23xx platform page.
Assisted-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Marco Casaroli <marco.casaroli@gmail.com>
