Input: auto-select INPUT for MAC_EMUMOUSEBTN option

Otherwise we'll ge the following build error:

  LD      .tmp_vmlinux1
drivers/built-in.o: In function `input_report_key':
include/linux/input.h:1158: undefined reference to `input_event'
    ...

Signed-off-by: Andreas Herrmann <aherrman@arcor.de>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>