Use the struct member w of the struct urelease_work directly instead of
casting it.

Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Link: https://lore.kernel.org/r/f0ed86d6d54ac0834bd2e161d172bf7bb5647cf7.1610683862.git.geliangtang@gmail.com


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