MIPS: BCM63xx: remove RSET_RNG register definitions

Now that these definitions have been moved to
drivers/char/hw_random/bcm63xx-rng.c where they belong to make the
driver standalone, we can safely remove these definitions from
bcm63xx_regs.h.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>