src/meta-openembedded:libgpiod: nherit python3native unconditionally

this recipe inherits python3native class conditionally, this condition
depends on a given packageconfig, however inherit ${VAR} syntax requires
VAR to be evaluated before inheriting it, therefore if someone appends
python3 to packageconfig via a bbappend, then the packageconfig will
become effective and add --enable-bindings-python to configure but
inherit wont evaluate correctly since the expression adding to
packageconfig

PACKAGECONFIG_append = " python3"

will be coming _after_ the inherit, and the builds will fail e.g.

| ../../../libgpiod-1.3/bindings/python/gpiodmodule.c:8:10: fatal error: Python.h: No such file or directory
|  #include <Python.h>

This will still mean that python3native is always inherited but the
effective configure option will be --disable-bindings-python and that
will do the right thing

See. openembedded/meta-openembedded#140

Signed-off-by: Khem Raj <raj.khem@gmail.com>