RDMA/siw: Add sendpage_ok() check to disable MSG_SPLICE_PAGES

RDMA/siw: Add sendpage_ok() check to disable MSG_SPLICE_PAGES

While running ISER over SIW, the initiator machine encounters a warning
from skb_splice_from_iter() indicating that a slab page is being used in
send_page. To address this, it is better to add a sendpage_ok() check
within the driver itself, and if it returns 0, then MSG_SPLICE_PAGES flag
should be disabled before entering the network stack.

A similar issue has been discussed for NVMe in this thread:
https://lore.kernel.org/all/20240530142417.146696-1-ofir.gal@volumez.com/

  WARNING: CPU: 0 PID: 5342 at net/core/skbuff.c:7140 skb_splice_from_iter+0x173/0x320
  Call Trace:
   tcp_sendmsg_locked+0x368/0xe40
   siw_tx_hdt+0x695/0xa40 [siw]
   siw_qp_sq_process+0x102/0xb00 [siw]
   siw_sq_resume+0x39/0x110 [siw]
   siw_run_sq+0x74/0x160 [siw]
   kthread+0xd2/0x100
   ret_from_fork+0x34/0x40
   ret_from_fork_asm+0x1a/0x30

Link: https://patch.msgid.link/r/20241007125835.89942-1-showrya@chelsio.com
Signed-off-by: Showrya M N <showrya@chelsio.com>
Signed-off-by: Potnuri Bharat Teja <bharat@chelsio.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>