Gate entropy injection through a dedicated configuration option

Entropy injection has specific testing requirements. Therefore it
should depend on a specific option.
diff --git a/include/mbedtls/check_config.h b/include/mbedtls/check_config.h
index 607deb9..c1450db 100644
--- a/include/mbedtls/check_config.h
+++ b/include/mbedtls/check_config.h
@@ -530,6 +530,17 @@
 #error "MBEDTLS_PSA_CRYPTO_STORAGE_C defined, but not all prerequisites"
 #endif
 
+#if defined(MBEDTLS_PSA_INJECT_ENTROPY) &&      \
+    !( defined(MBEDTLS_PSA_CRYPTO_STORAGE_C) && \
+       defined(MBEDTLS_ENTROPY_NV_SEED) )
+#error "MBEDTLS_PSA_INJECT_ENTROPY defined, but not all prerequisites"
+#endif
+
+#if defined(MBEDTLS_PSA_INJECT_ENTROPY) &&              \
+    !defined(MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES)
+#error "MBEDTLS_PSA_INJECT_ENTROPY is not compatible with actual entropy sources"
+#endif
+
 #if defined(MBEDTLS_PSA_ITS_FILE_C) && \
     !defined(MBEDTLS_FS_IO)
 #error "MBEDTLS_PSA_ITS_FILE_C defined, but not all prerequisites"