staging: octeon: Fix return type of cvm_oct_xmit and cvm_oct_xmit_pow

staging: octeon: Fix return type of cvm_oct_xmit and cvm_oct_xmit_pow

The ndo_start_xmit field in net_device_ops is expected to be of type
netdev_tx_t (*ndo_start_xmit)(struct sk_buff *skb, struct net_device *dev).

The mismatched return type breaks forward edge kCFI since the underlying
function definition does not match the function hook definition.

The return type of cvm_oct_xmit and cvm_oct_xmit_pow should be changed
from int to netdev_tx_t.

Link: https://github.com/ClangBuiltLinux/linux/issues/1703
Cc: llvm@lists.linux.dev
Reported-by: Dan Carpenter <error27@gmail.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Nathan Huckleberry <nhuck@google.com>
Link: https://lore.kernel.org/r/20220914211057.423617-1-nhuck@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>