net/mlx5: HWS, fix definer's HWS_SET32 macro for negative offset

When bit offset for HWS_SET32 macro is negative,
UBSAN complains about the shift-out-of-bounds:

  UBSAN: shift-out-of-bounds in
  drivers/net/ethernet/mellanox/mlx5/core/steering/hws/definer.c:177:2
  shift exponent -8 is negative

Fixes: 74a778b4 ("net/mlx5: HWS, added definers handling")
Signed-off-by: Yevgeny Kliteynik <kliteyn@nvidia.com>
Reviewed-by: Erez Shitrit <erezsh@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20250102181415.1477316-12-tariqt@nvidia.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>