spi: loopback-test: fix up const pointer issue in rx_ranges_cmp()

When a list head is a const pointer, the list entry for that head also
must remain a const pointer, otherwise we are just "throwing it away"
for no good reason.  Fix this up by properly marking these structures as
const.

Cc: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://patch.msgid.link/2025052213-semifinal-sublevel-d631@gregkh
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: gregkh

drivers/spi/spi-loopback-test.c

@@ -494,8 +494,8 @@ struct rx_ranges {
 static int rx_ranges_cmp(void *priv, const struct list_head *a,
 			 const struct list_head *b)
 {
-	struct rx_ranges *rx_a = list_entry(a, struct rx_ranges, list);
-	struct rx_ranges *rx_b = list_entry(b, struct rx_ranges, list);
+	const struct rx_ranges *rx_a = list_entry(a, struct rx_ranges, list);
+	const struct rx_ranges *rx_b = list_entry(b, struct rx_ranges, list);
 
 	if (rx_a->start > rx_b->start)
 		return 1;