ibmvnic: Add stat for tx direct vs tx batched

ibmvnic: Add stat for tx direct vs tx batched

[ Upstream commit 2ee73c54a615b74d2e7ee6f20844fd3ba63fc485 ]

Allow tracking of packets sent with send_subcrq direct vs
indirect. `ethtool -S <dev>` will now provide a counter
of the number of uses of each xmit method. This metric will
be useful in performance debugging.

Signed-off-by: Nick Child <nnac123@linux.ibm.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20241001163531.1803152-1-nnac123@linux.ibm.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Stable-dep-of: bdf5d13aa05e ("ibmvnic: Don't reference skb after sending to VIOS")
Signed-off-by: Sasha Levin <sashal@kernel.org>