ibmvnic: Remove duplicate memory barriers in tx

send_subcrq_[in]direct() already has a dma memory barrier.
Remove the earlier one.

Signed-off-by: Nick Child <nnac123@linux.ibm.com>
Link: https://patch.msgid.link/20240807211809.1259563-5-nnac123@linux.ibm.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>