netpoll: Eliminate redundant assignment

The assignment of zero to udph->check is unnecessary as it is
immediately overwritten in the subsequent line. Remove the redundant
assignment.

Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Joe Damato <jdamato@fastly.com>
Link: https://patch.msgid.link/20250319-netpoll_nit-v1-1-a7faac5cbd92@debian.org


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