libgpiod: make Python bindings optional

The python3-light dependency gets lugged even with the package disabled,
so this commit makes python3-light a conditional dependency, similar to
gensio in 0c245fd.

Signed-off-by: Ernestas Kulik <ernestas.k@iconn-networks.com>

Author: ernestask

libs/libgpiod/Makefile

@@ -90,7 +90,7 @@ define Package/python3-gpiod
   SUBMENU:=Python
   TITLE:=Python bindings for libgpiod
   URL:=https://git.kernel.org/pub/scm/libs/libgpiod/libgpiod.git
-  DEPENDS:=+python3-light +libgpiod
+  DEPENDS:=+PACKAGE_python3-gpiod:python3-light +libgpiod
 endef
 
 define Package/python3-gpiod/description