net/mlx5e: psp: Fix invalid access on PSP dev registration fail

net/mlx5e: psp: Fix invalid access on PSP dev registration fail

priv->psp->psp is initialized with the PSP device as returned by
psp_dev_create(). This could also return an error, in which case a
future psp_dev_unregister() will result in unpleasantness.

Avoid that by using a local variable and only saving the PSP device when
registration succeeds.

In case psp_dev_create() fails, priv->psp and steering structs are left
in place, but they will be inert. The unchecked access of priv->psp in
mlx5e_psp_offload_handle_rx_skb() won't happen because without a PSP
device, there can be no SAs added and therefore no packets will be
successfully decrypted and be handed off to the SW handler.

Fixes: 89ee2d92f66c ("net/mlx5e: Support PSP offload functionality")
Signed-off-by: Cosmin Ratiu <cratiu@nvidia.com>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20260504181100.269334-2-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>