ethtool: Don't check for NULL info in prepare_data callbacks

ethtool: Don't check for NULL info in prepare_data callbacks

Since commit f946270d05c2 ("ethtool: netlink: always pass genl_info to
.prepare_data") the info argument of prepare_data callbacks is never
NULL. Remove checks present in callback implementations.

Link: https://lore.kernel.org/netdev/20240703121237.3f8b9125@kernel.org/
Signed-off-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20240731-prepare_data-null-check-v1-1-627f2320678f@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>