[crypto]fix build when MBEDTLS_X509_CSR_WRITE_C not configure (#19754)

add MBEDTLS_X509_CSR_WRITE_C conditional build

Signed-off-by: Qingsong Gou <gouqs@hotmail.com>

src/crypto/CHIPCryptoPALmbedTLS.cpp

@@ -1036,6 +1036,7 @@ P256Keypair::~P256Keypair()
 
 CHIP_ERROR P256Keypair::NewCertificateSigningRequest(uint8_t * out_csr, size_t & csr_length) const
 {
+#if defined(MBEDTLS_X509_CSR_WRITE_C)
  CHIP_ERROR error = CHIP_NO_ERROR;
  int result = 0;
  size_t out_length;
@@ -1083,6 +1084,10 @@ CHIP_ERROR P256Keypair::NewCertificateSigningRequest(uint8_t * out_csr, size_t &
 
  _log_mbedTLS_error(result);
  return error;
+#else
+ ChipLogError(Crypto, "MBEDTLS_X509_CSR_WRITE_C is not enabled. CSR cannot be created");
+ return CHIP_ERROR_UNSUPPORTED_CHIP_FEATURE;
+#endif
 }
 
 CHIP_ERROR VerifyCertificateSigningRequest(const uint8_t * csr_buf, size_t csr_length, P256PublicKey & pubkey)