board: ti: Kconfig: Correct invalid Kconfig syntax

board: ti: Kconfig: Correct invalid Kconfig syntax

Kconfig does not support using 'select' to select a 'choice'. A choice
can be configured by either setting the choice symbol to 'y' in a
configuration file or by setting a 'default' of the choice.

In board/ti/*/Kconfig the SOC_K3_* choice is already set to 'y' in their
corresponding configs/*_defconfig file. So remove selecting it.

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