Description: mk: use make silent flag to print HTML doc version

Depending on the environment, make might echo the command being ran.
In mk/rte.sdkdoc.mk make is used to print the DPDK version to be
piped to doxygen. This causes the following to be written:

<div id="projectname">DPDK
&#160;<span id="projectnumber">/usr/bin/make-f/build/dpdk-jYjqnr/dpdk-16.11.2/mk/rte.sdkconfig.mkshowversion</span>
</div>

Use -s (--silent) to prevent echoing.

Origin: http://dpdk.org/dev/patchwork/patch/25673/
Forwarded: yes
Author: Luca Boccassi <luca.boccassi@gmail.com>
Last-Update: 2017-06-24
---
 mk/rte.sdkdoc.mk | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mk/rte.sdkdoc.mk
+++ b/mk/rte.sdkdoc.mk
@@ -71,7 +71,7 @@ api-html: api-html-clean
 	$(Q)mkdir -p $(RTE_OUTPUT)/doc/html
 	$(Q)(cat $(RTE_SDK)/doc/api/doxy-api.conf     && \
 	    printf 'PROJECT_NUMBER = '                && \
-	                      $(MAKE) -rR showversion && \
+	                     $(MAKE) -rRs showversion && \
 	    echo OUTPUT_DIRECTORY = $(RTE_OUTPUT)/doc && \
 	    echo HTML_OUTPUT      = html/api          && \
 	    echo GENERATE_HTML    = YES               && \