ichiic: use bool for one-bit wide bit-fields

A one-bit wide bit-field can take only the values 0 and -1. Clang 16
introduced a warning that "implicit truncation from 'int' to a one-bit
wide bit-field changes value from 1 to -1". Fix by using c99 bool.

Reported by: Clang
Reviewed by: emaste, wulf
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D39665