trace-cmd: Use "exists" instead of "exist"

As a native English speaker, I find that the words "file_exists" and
"dir_exists" sounds better to the ear than "file_exist" and "dir_exist".
As "exist" is for the plural, and "exists" is for the singular.

Link: http://lore.kernel.org/linux-trace-devel/20200414014611.146422111@goodmis.org

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
4 files changed