gpio: xlp: Remove Netlogic XLP variants

Netlogic XLP was removed in commit 95b8a5e0

 ("MIPS: Remove NETLOGIC
support"). With those gone, the single platform left to support is
Cavium ThunderX2. Remove all the Netlogic variants and DT support.

For simplicity, the existing kconfig name is retained.

Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Bartosz Golaszewski <brgl@bgdev.pl>
Cc: linux-gpio@vger.kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>