net/packet: Remove redundant assignment to ret

Variable ret is set to '0' or '-EBUSY', but this value is never read
as it is not used later on, hence it is a redundant assignment and
can be removed.

Clean up the following clang-analyzer warning:

net/packet/af_packet.c:3936:4: warning: Value stored to 'ret' is never
read [clang-analyzer-deadcode.DeadStores].

net/packet/af_packet.c:3933:4: warning: Value stored to 'ret' is never
read [clang-analyzer-deadcode.DeadStores].

No functional change.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>