perf tools: Fix a typo in a variable name in the Documentation Makefile

This patch fix a spelling typo in a variable name in the Documentation Makefile.
Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20190801032812.25018-1-standby24x7@gmail.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/Makefile

@@ -242,7 +242,7 @@ $(OUTPUT)doc.dep : $(wildcard *.txt) build-docdep.perl
 	$(PERL_PATH) ./build-docdep.perl >$@+ $(QUIET_STDERR) && \
 	mv $@+ $@
 
--include $(OUPTUT)doc.dep
+-include $(OUTPUT)doc.dep
 
 _cmds_txt = cmds-ancillaryinterrogators.txt \
 	cmds-ancillarymanipulators.txt \