net: phy: broadcom: Update Auxiliary Control Register macros

Add the RXD-to-RXC skew (delay) time bit in the Miscellaneous Control
shadow register and a mask for the shadow selector field.

Remove a re-definition of MII_BCM54XX_AUXCTL_SHDWSEL_AUXCTL.

Signed-off-by: Xo Wang <xow@google.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: David S. Miller <davem@davemloft.net>