iommu/mediatek: Fix a build fail of m4u_type

The commit ("iommu/mediatek: Enlarge the validate PA range
for 4GB mode") introduce the following build error:

   drivers/iommu/mtk_iommu.c: In function 'mtk_iommu_hw_init':
>> drivers/iommu/mtk_iommu.c:536:30: error: 'const struct mtk_iommu_data'
 has no member named 'm4u_type'; did you mean 'm4u_dom'?
     if (data->enable_4GB && data->m4u_type != M4U_MT8173) {

This patch fix it, use "m4u_plat" instead of "m4u_type".
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Yong Wu <yong.wu@mediatek.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/mtk_iommu.c

@@ -533,7 +533,7 @@ static int mtk_iommu_hw_init(const struct mtk_iommu_data *data)
 
 	writel_relaxed(F_MMU_IVRP_PA_SET(data->protect_base, data->enable_4GB),
 		       data->base + REG_MMU_IVRP_PADDR);
-	if (data->enable_4GB && data->m4u_type != M4U_MT8173) {
+	if (data->enable_4GB && data->m4u_plat != M4U_MT8173) {
 		/*
 		 * If 4GB mode is enabled, the validate PA range is from
 		 * 0x1_0000_0000 to 0x1_ffff_ffff. here record bit[32:30].