HV: crypto lib code clean up

Modify and simplify the code:
1. Removed unused definitions and pre-compile code
2. remove test code
3. Code style

Signed-off-by: Chen, Gang G <gang.g.chen@intel.com>

hypervisor/lib/crypto/mbedtls/hkdf.c

@@ -18,17 +18,8 @@
  *
  *  This file is part of mbed TLS (https://tls.mbed.org)
  */
-#if !defined(MBEDTLS_CONFIG_FILE)
-#include "mbedtls/config.h"
-#else
-#include MBEDTLS_CONFIG_FILE
-#endif
 
-#if defined(MBEDTLS_HKDF_C)
-
-#include <string.h>
-#include "mbedtls/hkdf.h"
-#include "mbedtls/platform_util.h"
+#include "hkdf.h"
 
 int mbedtls_hkdf( const mbedtls_md_info_t *md, const unsigned char *salt,
                   size_t salt_len, const unsigned char *ikm, size_t ikm_len,
@@ -188,5 +179,3 @@ exit:
 
     return( ret );
 }
-
-#endif /* MBEDTLS_HKDF_C */