serial: samsung: only use earlycon for console

A configuration that enables earlycon but not the core console
code causes a link error:

  drivers/built-in.o: In function `setup_earlycon':
  drivers/tty/serial/earlycon.c:70: undefined reference to `uart_parse_earlycon'

That error can be triggered by the newly added samsung earlycon support,
which is missing a 'select' statement.

As suggested by Peter Hurley, solves the problem by moving the
'select SERIAL_EARLYCON' statement to the samsung console driver
option, as it is done by all other console drivers.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: b94ba032 ("serial: samsung: Add support for early console")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>