drivers: net: cpsw: add support to have phy address from cpsw platform data

Some platforms like AM437x have different EVMs with different phy addresses,
so this patch adds support for passing phy address via cpsw plaform data.
Also renamed phy_id to phy_addr so better understanding of the code.

Reviewed-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
[trini: Update BuR am335x_igep0033 pcm051_rev3 pcm051_rev1 cm_t335
pengwyn boards]
Signed-off-by: Tom Rini <trini@ti.com>