net: macb: fix build errors when linux/phy*.h is removed from net/dsa.h

drivers/net/ethernet/cadence/macb.h:862:33: sparse: expected ; at end of declaration
drivers/net/ethernet/cadence/macb.h:862:33: sparse: Expected } at end of struct-union-enum-specifier
drivers/net/ethernet/cadence/macb.h:862:33: sparse: got phy_interface
drivers/net/ethernet/cadence/macb.h:877:1: sparse: Expected ; at the end of type declaration
drivers/net/ethernet/cadence/macb.h:877:1: sparse: got }
In file included from drivers/net/ethernet/cadence/macb_pci.c:29:0:
drivers/net/ethernet/cadence/macb.h:862:2: error: unknown type name 'phy_interface_t'
     phy_interface_t  phy_interface;
     ^~~~~~~~~~~~~~~

Add linux/phy.h to macb.h

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>