Explicitly enable built-in entropy in sample and test configs

Now that built-in entropy is a positive option
`MBEDTLS_PSA_BUILTIN_GET_ENTROPY` instead of a negative option
`MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES`, it needs to be enabled explicitly in
sample and test configurations.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/configs/crypto-config-ccm-psk-tls1_2.h b/configs/crypto-config-ccm-psk-tls1_2.h
index e4de8b3..163520e 100644
--- a/configs/crypto-config-ccm-psk-tls1_2.h
+++ b/configs/crypto-config-ccm-psk-tls1_2.h
@@ -31,15 +31,9 @@
 
 #define MBEDTLS_CTR_DRBG_C
 #define MBEDTLS_ENTROPY_C
+#define MBEDTLS_PSA_BUILTIN_GET_ENTROPY
 
 /* Save RAM at the expense of ROM */
 #define MBEDTLS_AES_ROM_TABLES
 
-/*
- * You should adjust this to the exact number of sources you're using: default
- * is the "platform_entropy_poll" source, but you may want to add other ones
- * Minimum is 2 for the entropy test suite.
- */
-#define MBEDTLS_ENTROPY_MAX_SOURCES 2
-
 #endif /* PSA_CRYPTO_CONFIG_H */