package/libiio: add missing backslash to python binding logic

Commit 5ac65831d5b6434dfa (package/libiio: drop python2 support) combined
two LIBIIO_CONF_OPTS lines, but forgot the backslash at the end of the line.
Fix that.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/libiio/libiio.mk

@@ -75,7 +75,7 @@ endif
 ifeq ($(BR2_PACKAGE_LIBIIO_BINDINGS_PYTHON),y)
 LIBIIO_DEPENDENCIES += host-python3-setuptools python3
 LIBIIO_CONF_OPTS += \
-	-DPYTHON_BINDINGS=ON
+	-DPYTHON_BINDINGS=ON \
 	-DPYTHON_EXECUTABLE=$(HOST_DIR)/bin/python3
 else
 LIBIIO_CONF_OPTS += -DPYTHON_BINDINGS=OFF