rtla: Make doc build optional

JIRA: https://issues.redhat.com/browse/RHEL-50869

commit 2201aea
Author: Shuah Khan <skhan@linuxfoundation.org>
Date:   Tue Jan 25 17:13:01 2022 -0700

    rtla: Make doc build optional

    rtla build fails due to doc build dependency on rst2man. Make
    doc build optional so rtla could be built without docs. Leave
    the install dependency on doc_install alone.

    Link: https://lkml.kernel.org/r/20220126001301.79096-1-skhan@linuxfoundation.org

    Acked-by: Daniel Bristot de Oliveira <bristot@kernel.org>
    Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
    Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>

Author: lclaudio

tools/tracing/rtla/Makefile

@@ -111,7 +111,7 @@ warnings: $(WARNINGS)
 	$(ERROR_OUT)
 endif
 
-rtla: $(OBJ) doc
+rtla: $(OBJ)
 	$(CC) -o rtla $(LDFLAGS) $(OBJ) $(LIBS)
 
 static: $(OBJ)