soc: silabs: Fix CMake test for soc family

Kconfig options need CONFIG_ prefix when tested for in CMakeLists.txt.

Fixes regression introduced in e90c89d45311aed6612113cf6bfdce652bba250d
that causes all apps to fail to initialize on Silabs socs.

Signed-off-by: Aksel Skauge Mellbye <aksel.mellbye@silabs.com>
1 file changed