boards: cc322xsf_launchxl: Do not assign promptless HAS_CC3220SDK sym

Assignments have no effect on promptless symbols. Flagged by
https://github.com/zephyrproject-rtos/zephyr/pull/20742

.

This symbol is (always) selected, in
soc/arm/ti_simplelink/cc32xx/Kconfig.soc.

Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>