phylib: Allow BCM63XX PHY to be selected only on BCM63XX.

This PHY is available integrated into BCM63xx series SOCs only.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
 drivers/net/phy/Kconfig |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
Acked-by: Florian Fainelli <ffainelli@freebox.fr>
Signed-off-by: David S. Miller <davem@conan.davemloft.net>