drivers/tty: ehv_bytechan fails to build as a module

ehv_bytechan is marked tristate but fails to build as a module:

drivers/tty/ehv_bytechan.c:363:1: error: type defaults to ‘int’ in declaration of ‘console_initcall’ [-Werror=implicit-int]

It doesn't make much sense for a console driver to be built as
a module, so change it to a bool.

Signed-off-by: Anton Blanchard <anton@samba.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Scott Wood <scottwood@freescale.com>