net: lpc32xx: connect MAC to phy with CONFIG_PHY_ADDR id

The lpc32xx_eth_phylib_init() function is capable to connect LPC32XX
MAC to some specified phy by phy id, by chance the single user of
lpc32xx_eth has CONFIG_PHY_ADDR set to 0, however other boards may
have non-zero CONFIG_PHY_ADDR value, fix it.

Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>
Acked-by: Albert ARIBAUD (3ADEV) <albert.aribaud@3adev.fr>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>