XIA: remove CONFIG_EXPERIMENTAL

The CONFIG_EXPERIMENTAL config has been removed from the kernel.
See commit `final removal of CONFIG_EXPERIMENTAL' by
Kees Cook <keescook@chromium.org>.
Change XDP type to harmonize Linux and Click XIA
Add support to NLM_F_* flags

Added flags: NLM_F_CREATE, NLM_F_EXCL, and NLM_F_REPLACE.

HID only enforces that NLM_F_CREATE and NLM_F_EXCL were requested
due to code complexity and lack of users for other combinations.