soc: silabs: Fix CMake test for soc family

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

Fixes regression introduced in e90c89d
that causes all apps to fail to initialize on Silabs socs.

Signed-off-by: Aksel Skauge Mellbye <[email protected]>

Author: asmellby

soc/silabs/common/CMakeLists.txt

@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: Apache-2.0
 
-if(SOC_FAMILY_SILABS_S0 OR SOC_FAMILY_SILABS_S1 OR SOC_FAMILY_SILABS_S2)
+if(CONFIG_SOC_FAMILY_SILABS_S0 OR CONFIG_SOC_FAMILY_SILABS_S1 OR CONFIG_SOC_FAMILY_SILABS_S2)
   zephyr_sources(soc.c)
 endif()