RDMA/irdma: avoid fortify-string warning in irdma_clr_wqes

Commit df8fc4e9 ("kbuild: Enable -fstrict-flex-arrays=3") triggers a
warning for fortified memset():

In function 'fortify_memset_chk',
    inlined from 'irdma_clr_wqes' at drivers/infiniband/hw/irdma/uk.c:103:4:
include/linux/fortify-string.h:493:25: error: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning]
  493 |                         __write_overflow_field(p_size_field, size);
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The problem here isthat the inner array only has four 8-byte elements, so
clearing 4096 bytes overflows that. As this structure is part of an outer
array, change the code to pass a pointer to the irdma_qp_quanta instead,
and change the size argument for readability, matching the comment above
it.

Fixes: 551c46ed ("RDMA/irdma: Add user/kernel shared libraries")
Link: https://lore.kernel.org/r/20230523111859.2197825-1-arnd@kernel.orgSigned-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/hw/irdma/uk.c

@@ -93,16 +93,18 @@ static int irdma_nop_1(struct irdma_qp_uk *qp)
  */
 void irdma_clr_wqes(struct irdma_qp_uk *qp, u32 qp_wqe_idx)
 {
-	__le64 *wqe;
+	struct irdma_qp_quanta *sq;
 	u32 wqe_idx;
 
 	if (!(qp_wqe_idx & 0x7F)) {
 		wqe_idx = (qp_wqe_idx + 128) % qp->sq_ring.size;
-		wqe = qp->sq_base[wqe_idx].elem;
+		sq = qp->sq_base + wqe_idx;
 		if (wqe_idx)
-			memset(wqe, qp->swqe_polarity ? 0 : 0xFF, 0x1000);
+			memset(sq, qp->swqe_polarity ? 0 : 0xFF,
+			       128 * sizeof(*sq));
 		else
-			memset(wqe, qp->swqe_polarity ? 0xFF : 0, 0x1000);
+			memset(sq, qp->swqe_polarity ? 0xFF : 0,
+			       128 * sizeof(*sq));
 	}
 }