kern/subr_intr: fix build with DEBUG on arm64/aarch64

[val_packett.cool]

Summary

Fixes the following error:

/usr/src/sys/kern/subr_intr.c:802:37: error: format specifies type 'unsigned int' but the argument has type 'intptr_t' (aka 'long') [-Werror,-Wformat]
            device_get_nameunit(dev), dev, xref);
                                           ^~~~

[andrew]

sys/kern/subr_intr.c

800–801 ↗

(On Diff #72192)

The normal way in the kernel is to cast to uintmax_t and use %jx.

[emaste]

sys/kern/subr_intr.c

800–801 ↗

(On Diff #72192)

Indeed, there is another instance of this same debugf earlier, with (uintmax_t).