leds: trigger: netdev: Remove NULL check before dev_{put, hold}

leds: trigger: netdev: Remove NULL check before dev_{put, hold}

The call netdev_{put, hold} of dev_{put, hold} will check NULL,
so there is no need to check before using dev_{put, hold},
remove it to silence the warnings:

./drivers/leds/trigger/ledtrig-netdev.c:291:3-10: WARNING: NULL check before dev_{put, hold} functions is not needed.
./drivers/leds/trigger/ledtrig-netdev.c:401:2-9: WARNING: NULL check before dev_{put, hold} functions is not needed.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=4929
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Link: https://lore.kernel.org/r/20230511070820.52731-1-yang.lee@linux.alibaba.com
Signed-off-by: Lee Jones <lee@kernel.org>