Correct the tablegen logic for MutualExclusions attribute checking.

Just because an attribute is a statement attribute doesn't mean it's
not also a declaration attribute. In Clang, there are not currently any
DeclOrStmtAttr attributes that require mutual exclusion checking, but
downstream clients discovered this issue.

GitOrigin-RevId: 028092eb613e5553ce0833878e7d36fcaf11fcb2
1 file changed