nb/intel/sandybridge: Set uninitialized run length

If the entire array is zero, then the length of the
longest zero run is the length of the array itself.

Found-by: Coverity Scan, CID 1229715
Signed-off-by: Jacob Garber <jgarber1@ualberta.ca>
Change-Id: Id23292087b14182448d70117915fb044e9c579f7
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32249
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/northbridge/intel/sandybridge/raminit_common.c

@@ -1142,6 +1142,7 @@ static struct run get_longest_zero_run(int *seq, int sz)
 		ret.middle = sz / 2;
 		ret.start = 0;
 		ret.end = sz;
+		ret.length = sz;
 		ret.all = 1;
 		return ret;
 	}