doc: Makefile: Remove the 'doxy-code' target

Identical with the 'doxy' target. Move the 'doxy-code' recipe over to
'doxy' and remove 'doxy-code'.

Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>
diff --git a/doc/Makefile b/doc/Makefile
index 2b953f6..4e41034 100644
--- a/doc/Makefile
+++ b/doc/Makefile
@@ -20,12 +20,10 @@
 # the i18n builder cannot share the environment and doctrees with the others
 I18NSPHINXOPTS  = $(PAPEROPT_$(PAPER)) $(SPHINXOPTS) .
 
-.PHONY: help clean content kconfig prep html dirhtml singlehtml pickle json htmlhelp qthelp devhelp epub latex latexpdf text man changes linkcheck doctest coverage gettext
+.PHONY: doxy help clean content kconfig prep html dirhtml singlehtml pickle json htmlhelp qthelp devhelp epub latex latexpdf text man changes linkcheck doctest coverage gettext
 
-doxy-code:
-	$(Q)(cat zephyr.doxyfile ; echo "STRIP_FROM_PATH=${ZEPHYR_BASE}" ) | doxygen -  2>&1 | tee doc.log
-
-doxy: doxy-code
+doxy:
+	$(Q)(cat zephyr.doxyfile ; echo "STRIP_FROM_PATH=${ZEPHYR_BASE}" ) | doxygen - 2>&1 | tee doc.log
 
 help:
 	@echo "Please use \`make <target>' where <target> is one of"