hwrng: bcm63xx - drop bcm_{readl,writel} macros

bcm_{readl,writel} macros expand to __raw_{readl,writel}, use these
directly such that we do not rely on the platform to provide these for
us. As a result, we no longer use bcm63xx_io.h, so remove that inclusion
too.

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