net: phy: bcm7xxx: fix spurious MDIO failures during workaround

Writing first to the AFE registers, and then the VCO, RCAL, RC_CAL
registers turned out to unveil some spurious MDIO read/write failures
which would make the workaround partially applied. The fix is to write
first to the VCO, RCAL, RC_CAL registers, and then write to the AFE
registers.

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