With kldxref from 10.0-2, this warnc() reports EFAULT, rendering the
output useless. However this is no longer reproducible after rebuilding
10.0-2 with recent unstable. Let's treat this warnc() as fatal so that
at least we know if/when trouble comes back.

It's probably related to offset types (Elf_Off / off_t). Unfortunately
I haven't been able to diagnose it:

$ kldxref -dv /tmp/t/
/tmp/t/drm2.ko
kldxref: ef_seg_read_rel(/tmp/t/drm2.ko): bad offset/len (4800000130808b48:33)
kldxref: error while reading /tmp/t/drm2.ko: Bad address

--- a/src/usr.sbin/kldxref/kldxref.c
+++ b/src/usr.sbin/kldxref/kldxref.c
@@ -230,7 +230,7 @@
 			parse_entry(&md, cval, &ef, kldname);
 		}
 		if (error)
-			warnc(error, "error while reading %s", filename);
+			errc(error, "error while reading %s", filename);
 		free(orgp);
 	} while(0);
 	EF_CLOSE(&ef);