board: ti: am64x: Add support for AM64B SK

The AM64x SR2.0 SK board uses "AM64B-SKEVM" as the EEPROM identifier.
This board is similar to the AM64x SKEVM except that it has a new
PMIC that will be enabled in the future and consequently could use a
different device tree file in the future.

For now we treat the board same as an AM64x SK.

Signed-off-by: Judith Mendez <jm@ti.com>
Acked-by: Andrew Davis <afd@ti.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>