Fix the same BIO_FLAGS macro definition

Also add comment to the public header to avoid
making another conflict in future.

Fixes #17545

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from #17546)

include/internal/bio.h

@@ -48,9 +48,9 @@ int bread_conv(BIO *bio, char *data, size_t datal, size_t *read);
  * BIO_FLAGS_KTLS_TX_CTRL_MSG means we are about to send a ctrl message next.
  * BIO_FLAGS_KTLS_RX means we are using ktls with this BIO for receiving.
  */
-# define BIO_FLAGS_KTLS_TX          0x800
 # define BIO_FLAGS_KTLS_TX_CTRL_MSG 0x1000
 # define BIO_FLAGS_KTLS_RX          0x2000
+# define BIO_FLAGS_KTLS_TX          0x4000
 
 /* KTLS related controls and flags */
 # define BIO_set_ktls_flag(b, is_tx) \

include/openssl/bio.h.in

@@ -209,6 +209,8 @@ extern "C" {
 # define BIO_FLAGS_NONCLEAR_RST  0x400
 # define BIO_FLAGS_IN_EOF        0x800
 
+/* the BIO FLAGS values 0x1000 to 0x4000 are reserved for internal KTLS flags */
+
 typedef union bio_addr_st BIO_ADDR;
 typedef struct bio_addrinfo_st BIO_ADDRINFO;