tty: xtensa/iss: use u8

Switch character types to u8. To conform to characters in the rest of
the tty layer.

Signed-off-by: "Jiri Slaby (SUSE)" <[e-mail]>
Cc: Chris Zankel <[e-mail]>
Cc: Max Filippov <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

arch/xtensa/platforms/iss/console.c

···
 	struct tty_port *port = &serial_port;
 	int i = 0;
 	int rd = 1;
-	unsigned char c;
+	u8 c;
 
 	while (simc_poll(0)) {
 		rd = simc_read(0, &c, 1);