net: phy: broadcom: extract register definitions

The Broadcom BCM54xx register definitions are shared between BCM54xx and
BCM7xx internal PHYs for which we are adding support. Extract these
register definitions and put them in include/linux/brcmphy.h for use by
the BCM7xxx internal PHY driver.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>