vsock/vmci: Remove redundant assignment to err

Variable 'err' is set to zero but this value is never read as it is
overwritten with a new value later on, hence it is a redundant
assignment and can be removed.

Clean up the following clang-analyzer warning:

net/vmw_vsock/vmci_transport.c:948:2: warning: Value stored to 'err' is
never read [clang-analyzer-deadcode.DeadStores]

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>