Bugfix
   * Fix build failure with MBEDTLS_RSA_C and MBEDTLS_PSA_CRYPTO_C but not
     MBEDTLS_USE_PSA_CRYPTO or MBEDTLS_PK_WRITE_C. Fixes #6408.
   * Fix build failure with MBEDTLS_RSA_C and MBEDTLS_PSA_CRYPTO_C but not
     MBEDTLS_PK_PARSE_C. Fixes #6409.