mbedtls_pem_write_buffer: Correctly report needed buffer size for all possible line lengths and counts

Signed-off-by: Jethro Beekman <jethro@fortanix.com>
diff --git a/tests/suites/test_suite_pem.data b/tests/suites/test_suite_pem.data
index 332cb79..a34aa91 100644
--- a/tests/suites/test_suite_pem.data
+++ b/tests/suites/test_suite_pem.data
@@ -16,6 +16,9 @@
 PEM write (exactly two lines + 1)
 mbedtls_pem_write_buffer:"-----START TEST-----\n":"-----END TEST-----\n":"000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F00":"-----START TEST-----\nAAECAwQFBgcICQoLDA0ODwABAgMEBQYHCAkKCwwNDg8AAQIDBAUGBwgJCgsMDQ4P\nAAECAwQFBgcICQoLDA0ODwABAgMEBQYHCAkKCwwNDg8AAQIDBAUGBwgJCgsMDQ4P\nAA==\n-----END TEST-----\n"
 
+PEM write length reporting
+mbedtls_pem_write_buffer_lengths
+
 PEM read (unencrypted, valid)
 mbedtls_pem_read_buffer:"^":"$":"^\nTWJlZCBUTFM=\n$":"":0:"4d62656420544c53"