intel_iommu: Fix for IQA reg read dropped DW field

intel_iommu: Fix for IQA reg read dropped DW field

If VT-D hardware supports scalable mode, Linux will set the IQA DW field
(bit11). In qemu, the vtd_mem_write and vtd_update_iq_dw set DW field well.
However, vtd_mem_read the DW field wrong because "& VTD_IQA_QS" dropped the
value of DW.
Replace "&VTD_IQA_QS" with "& (VTD_IQA_QS | VTD_IQA_DW_MASK)" could save
the DW field.

Test patch as below:

config the "x-scalable-mode" option:
"-device intel-iommu,caching-mode=on,x-scalable-mode=on,aw-bits=48"

After Linux OS boot, check the IQA_REG DW Field by usage 1 or 2:

1. IOMMU_DEBUGFS:
Before fix:
cat /sys/kernel/debug/iommu/intel/iommu_regset |grep IQA
IQA             	0x90		0x00000001001da001

After fix:
cat /sys/kernel/debug/iommu/intel/iommu_regset |grep IQA
IQA             	0x90		0x00000001001da801

Check DW field(bit11) is 1.

2. devmem2 read the IQA_REG (offset 0x90):
Before fix:
devmem2 0xfed90090
/dev/mem opened.
Memory mapped at address 0x7f72c795b000.
Value at address 0xFED90090 (0x7f72c795b090): 0x1DA001

After fix:
devmem2 0xfed90090
/dev/mem opened.
Memory mapped at address 0x7fc95281c000.
Value at address 0xFED90090 (0x7fc95281c090): 0x1DA801

Check DW field(bit11) is 1.

Signed-off-by: yeeli <seven.yi.lee@gmail.com>
Message-Id: <20240725031858.1529902-1-seven.yi.lee@gmail.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>