soc: bcm: brcmstb: biuctrl: Update layout for A72 on 7211

The BIUCTRL layout is a little different on 7211 which is equipped with
a Cortex-A72, account for those register offset differences. We will
match 7211 specifically in a subsequent commit.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>