hw/riscv/riscv-iommu: Fix PPN field of Translation-reponse register

The original implementation incorrectly performed a bitwise AND
operation between the PPN of iova and PPN Mask, leading to an
incorrect PPN field in Translation-reponse register.

The PPN of iova should be set entirely in the PPN field of
Translation-reponse register.

Also remove the code that was used to clear S field since this
field is already zero.

Signed-off-by: Nutty Liu <liujingqi@lanxincomputing.com>
Reviewed-by: Tomasz Jeznach <tjeznach@rivosinc.com>
Message-ID: <20250605124848.1248-1-liujingqi@lanxincomputing.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

hw/riscv/riscv-iommu.c

@@ -1935,11 +1935,7 @@ static void riscv_iommu_process_dbg(RISCVIOMMUState *s)
             iova = RISCV_IOMMU_TR_RESPONSE_FAULT | (((uint64_t) fault) << 10);
         } else {
             iova = iotlb.translated_addr & ~iotlb.addr_mask;
-            iova >>= TARGET_PAGE_BITS;
+            iova = set_field(0, RISCV_IOMMU_TR_RESPONSE_PPN, PPN_DOWN(iova));
-            iova &= RISCV_IOMMU_TR_RESPONSE_PPN;
-
-            /* We do not support superpages (> 4kbs) for now */
-            iova &= ~RISCV_IOMMU_TR_RESPONSE_S;
         }
         riscv_iommu_reg_set64(s, RISCV_IOMMU_REG_TR_RESPONSE, iova);
     }