board: ti: Add dependency from TARGET selection to SOC

board: ti: Add dependency from TARGET selection to SOC

Currently the K3 selection for TARGET boards does not depend on the SoC
for which it is based. This leds to the odd ability to select for instance
both SOC_K3_AM625 and TARGET_J721E_A72_EVM.

To fix this the target choice should depend on the matching SOC config.

Signed-off-by: Andrew Davis <afd@ti.com>
Reviewed-by: Neha Malcom Francis <n-francis@ti.com>