net: lan966x: Remove a useless test in lan966x_ptp_add_trap()

vcap_alloc_rule() can't return NULL.

So remove some dead-code

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/27992ffcee47fc865ce87274d6dfcffe7a1e69e0.1670873784.git.christophe.jaillet@wanadoo.fr


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