selftests: drv-net: fix RPS mask handling in toeplitz test

selftests: drv-net: fix RPS mask handling in toeplitz test

The toeplitz.py test passed the hex mask without "0x" prefix (e.g.,
"300" for CPUs 8,9). The toeplitz.c strtoul() call wrongly parsed this
as decimal 300 (0x12c) instead of hex 0x300.

Pass the prefixed mask to toeplitz.c, and the unprefixed one to sysfs.

Fixes: 9cf9aa77a1f6 ("selftests: drv-net: hw: convert the Toeplitz test to Python")
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/20260112173715.384843-2-gal@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>