module_param: remove support for bool parameters which are really int.

module_param(bool) used to counter-intuitively take an int.  In
fddd5201

 (mid-2009) we allowed bool or int/unsigned int using a messy
trick.

This eliminates that code (though leaves the flags field in the struct,
for impending use).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>