selftests/ftrace: Fix requirement check of README file

The selftest for ftrace checks some features by checking if the README has
text that states the feature is supported by that kernel. Unfortunately,
this check gives false positives because it many not be checked if there's
spaces in the string to check. This is due to the compare between the
required variable with the ":README" string stripped, because neither has
quotes around them.

Link: https://lkml.kernel.org/r/20210820204742.087177341@goodmis.org

Cc: "Tzvetomir Stoyanov" <tz.stoyanov@gmail.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: linux-kselftest@vger.kernel.org
Cc: stable@vger.kernel.org
Fixes: 1b8eec51 ("selftests/ftrace: Support ":README" suffix for requires")
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

tools/testing/selftests/ftrace/test.d/functions

@@ -137,7 +137,7 @@ check_requires() { # Check required files and tracers
                 echo "Required tracer $t is not configured."
                 exit_unsupported
             fi
-        elif [ $r != $i ]; then
+        elif [ "$r" != "$i" ]; then
             if ! grep -Fq "$r" README ; then
                 echo "Required feature pattern \"$r\" is not in README."
                 exit_unsupported