net: phy: add support for TI DP83561-SP phy

Add support for the TI DP83561-SP Gigabit ethernet phy device.

The dp83561-sp is a radiation hardened space grade gigabit ethernet
PHY. It has been tested for single event latch upto 121 MeV, the
critical reliability parameter for space designs. It interfaces directly to
twisted pair media through an external transformer. And the device also
interfaces directly to the MAC layer through Reduced GMII (RGMII) and MII.

DP83867, DP83869 and DP83561-SP, all these parts support 1000Base-T/
100Base-TX/ and 10Base-Te standards and have similar register map for
the core functionality.

The data sheet for this part is at https://www.ti.com/product/DP83561-SP

Signed-off-by: Hari Nagalla <hnagalla@ti.com>
Signed-off-by: Geet Modi <geet.modi@ti.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20211118102532.9835-1-hnagalla@ti.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>