rtc: pic32: allow driver to be compiled with COMPILE_TEST

rtc: pic32: allow driver to be compiled with COMPILE_TEST

This driver currently only supports builds against a PIC32 target. Now
that commit ed65ae9f6c6b ("rtc: 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>
Link: https://patch.msgid.link/20260222-rtc-pic32-v1-1-3f8eb654a34d@redhat.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>