phylink: require valid state argument to phylink_validate_mask_caps()

state is deferenced earlier in the function, the NULL check
is pointless. Since we don't have any crash reports presumably
it's safe to assume state is not NULL.

Fixes: f392a184 ("net: phylink: provide phylink_validate_mask_caps() helper")
Reviewed-by: Sean Anderson <sean.anderson@seco.com>
Link: https://lore.kernel.org/r/20221025185126.1720553-1-kuba@kernel.org


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