libtraceevent: Rename "ok" to "token_has_paren" in process_sizeof()

The "ok" variable is set to true if at the end of the if/else blocks the
token contains the last element of "sizeof(..)", which would be that ")"
parenthesis. Calling it "ok" is meaningless and confusing.

Call the variable what it is for "token_has_paren". That will make the
logic much easier to understand.

Link: https://lore.kernel.org/linux-trace-devel/20230324200924.287521-4-rostedt@goodmis.org

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>