makefs: remove CD9660MAXPATH #define

It was used only in constructing the host path that contains file
content, which is not related to anything CD9660-specific. PATH_MAX is
the appropriate limit. See OpenBSD commit 299d8950f319.

Obtained from: OpenBSD
Sponsored by: The FreeBSD Foundation

(cherry picked from commit 2f11df63374d279238e4836125a81fa2c5234730)