tracing: Check operator stack capacity before pushing

In the Linux kernel, the following vulnerability has been resolved:

tracing: Check operator stack capacity before pushing

predicate_parse() uses the first operator stack entry before processing
any opening parentheses. A push then increments top before writing.
The existing check still permits that write when top already points to
the last allocated entry, which can access beyond the operator stack.

Reject the push when top reaches the last allocated entry.