tty: baudrate: Explicit usage of B0 for encoding input baudrate

Function tty_termios_input_baud_rate() checks IBSHIFT & CBAUD against B0
constant to determinate if input speed equals to output speed. So do same
B0 check also in tty_termios_encode_baud_rate() function to make these two
functions compatible.

Currently macro B0 is defined to 0 so there is no functional change.

This change just make code more explicit to show that Bnnn constants are
stored in CBAUD.

Signed-off-by: Pali Rohár <pali@kernel.org>
Link: https://lore.kernel.org/r/20210927133516.8671-1-pali@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/tty_baudrate.c

@@ -154,7 +154,7 @@ void tty_termios_encode_baud_rate(struct ktermios *termios,
 	termios->c_ospeed = obaud;
 
 #ifdef IBSHIFT
-	if ((termios->c_cflag >> IBSHIFT) & CBAUD)
+	if (((termios->c_cflag >> IBSHIFT) & CBAUD) != B0)
 		ibinput = 1;	/* An input speed was specified */
 #endif
 #ifdef BOTHER