Suppress cppcheck invalidSyntax warninigs

For some reason cppcheck 1.90 is generating an invalidSyntax warning
when the BF64_SET macro is used in the zstream source. The same
warning is not reported by cppcheck 2.3, nor is their any evident
problem with the expanded macro. This appears to be an issue with
this version of cppcheck. This commit annotates the source to suppress
the warning.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #11700