add a public_config in the efr32_mbedtls_config source set to fix a chain of define issue that led to MBEDTLS_USE_PSA_CRYPTO not being defined in the GSDK build section (#26810)

diff --git a/third_party/silabs/efr32_sdk.gni b/third_party/silabs/efr32_sdk.gni
index 5b5d4f2..ecd1e30 100644
--- a/third_party/silabs/efr32_sdk.gni
+++ b/third_party/silabs/efr32_sdk.gni
@@ -540,6 +540,7 @@
       "${chip_root}/src/platform/silabs/efr32/psa_crypto_config.h",
     ]
 
+    public_configs = [ "${chip_root}/src:includes" ]
     public_deps = [ "${chip_root}/src/crypto:crypto_buildconfig" ]
   }