pinctrl: pic32: allow driver to be compiled with COMPILE_TEST

pinctrl: pic32: allow driver to be compiled with COMPILE_TEST

This driver currently only supports builds against a PIC32 target. Now
that commit b8694faa1a0f ("pinctrl: pic32: update include to use pic32.h
from platform_data") is merged, it's possible to compile this driver on
other architectures.

To avoid future breakage of this driver in the future, let's update the
Kconfig so that it can be built with COMPILE_TEST enabled on all
architectures.

Signed-off-by: Brian Masney <bmasney@redhat.com>
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>