selftests: drv-net: fix RPS mask handling for high CPU numbers

The RPS bitmask bounds check uses ~(RPS_MAX_CPUS - 1) which equals ~15 =
0xfff0, only allowing CPUs 0-3.

Change the mask to ~((1UL << RPS_MAX_CPUS) - 1) = ~0xffff to allow CPUs
0-15.

Fixes: 5ebfb4c ("selftests/net: toeplitz test")
Reviewed-by: Nimrod Oren <noren@nvidia.com>
Signed-off-by: Gal Pressman <gal@nvidia.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20260112173715.384843-3-gal@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: gal-pressman

tools/testing/selftests/drivers/net/hw/toeplitz.c

@@ -485,8 +485,8 @@ static void parse_rps_bitmap(const char *arg)
 
 	bitmap = strtoul(arg, NULL, 0);
 
-	if (bitmap & ~(RPS_MAX_CPUS - 1))
-		error(1, 0, "rps bitmap 0x%lx out of bounds 0..%lu",
+	if (bitmap & ~((1UL << RPS_MAX_CPUS) - 1))
+		error(1, 0, "rps bitmap 0x%lx out of bounds, max cpu %lu",
 		      bitmap, RPS_MAX_CPUS - 1);
 
 	for (i = 0; i < RPS_MAX_CPUS; i++)