serial: core, move termios handling to uart_startup

We should not fiddle with speed and cflags in .dtr_rts hook. Actually
we might not have tty at that moment already.

So move the console cflag copy and speed setup into uart_startup.
Actually the speed setup is already there, but we need to call it
unconditionally (uart_startup is called from uart_open with hw_init =
0).

This means we move uart_change_speed before dtr/rts setup in .dtr_rts.
But this should not matter as the setup should be called after
uart_change_speed anyway.
Before:                             After:
dtr/rts setup (dtr_rts)             uart_change_speed (startup)
uart_change_speed (update_termios)  dtr/rts setup (dtr_rts)
dtr/rts setup (update_termios)      dtr/rts setup (update_termios)

The second setup will dismiss with the next patch.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>