add a public_config in the efr32_mbedtls_config source set to fix a c…

…hain of define issue that led to MBEDTLS_USE_PSA_CRYPTO not being defined in the GSDK build section (#26810)

third_party/silabs/efr32_sdk.gni

@@ -540,6 +540,7 @@ template("efr32_sdk") {
       "${chip_root}/src/platform/silabs/efr32/psa_crypto_config.h",
     ]
 
+    public_configs = [ "${chip_root}/src:includes" ]
     public_deps = [ "${chip_root}/src/crypto:crypto_buildconfig" ]
   }