phy: cadence: Sierra: Create PHY only for "phy" or "link" sub-nodes

Cadence Sierra PHY driver registers PHY using devm_phy_create()
for all sub-nodes of Sierra device tree node. However Sierra device
tree node can have sub-nodes for the various clocks in addtion to the
PHY. Use devm_phy_create() only for nodes with name "phy" (or "link"
for old device tree) which represent the actual PHY.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Aswath Govindraju <a-govindraju@ti.com>