Remove MBEDTLS_ECDH_C from baremetal configuration

Baremetal uses the tinyCrypt implementation of ECDHE.
diff --git a/configs/baremetal.h b/configs/baremetal.h
index 5c185d2..0bdee4f 100644
--- a/configs/baremetal.h
+++ b/configs/baremetal.h
@@ -46,7 +46,6 @@
 #define MBEDTLS_PK_C
 #define MBEDTLS_PK_PARSE_C
 #define MBEDTLS_PK_WRITE_C
-#define MBEDTLS_ECDH_C
 #define MBEDTLS_ECDSA_C
 #define MBEDTLS_ECP_C
 #define MBEDTLS_ECP_DP_SECP256R1_ENABLED