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/[email protected]

Acked-by: Daniel Bristot de Oliveira <[email protected]>
Signed-off-by: Shuah Khan <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: shuahkh

tools/tracing/rtla/Makefile

@@ -59,7 +59,7 @@ endif
 .PHONY:	all
 all:	rtla
 
-rtla: $(OBJ) doc
+rtla: $(OBJ)
 	$(CC) -o rtla $(LDFLAGS) $(OBJ) $(LIBS)
 
 static: $(OBJ)