arm64: dts: ti: k3-j7200-common-proc-board: Correct the name of io expander on main_i2c1

J7200 main_i2c1 is connected to the i2c bus on the CPB marked as main_i2c3

The i2c1 devices on the CPB are _not_ connected to the SoC, they are not
usable with the J7200 SOM.

Correct the expander name from exp4 to exp3 and at the same time add the
line names as well.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
Link: https://lore.kernel.org/r/20201120073533.24486-3-peter.ujfalusi@ti.com