iommu/vt-d: Remove unused dmar_msi_read

dmar_msi_read() has been unused since 2022 in
commit cf8e8658100d ("arch: Remove Itanium (IA-64) architecture")

Remove it.

(dmar_msi_write still exists and is used once).

Signed-off-by: Dr. David Alan Gilbert <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Lu Baolu <[e-mail]>
Signed-off-by: Joerg Roedel <[e-mail]>

drivers/iommu/intel/dmar.c

···
 	raw_spin_unlock_irqrestore(&iommu->register_lock, flag);
 }
 
-void dmar_msi_read(int irq, struct msi_msg *msg)
-{
-	struct intel_iommu *iommu = irq_get_handler_data(irq);
-	int reg = dmar_msi_reg(iommu, irq);
-	unsigned long flag;
-
-	raw_spin_lock_irqsave(&iommu->register_lock, flag);
-	msg->data = readl(iommu->reg + reg + 4);
-	msg->address_lo = readl(iommu->reg + reg + 8);
-	msg->address_hi = readl(iommu->reg + reg + 12);
-	raw_spin_unlock_irqrestore(&iommu->register_lock, flag);
-}
-
 static int dmar_fault_do_one(struct intel_iommu *iommu, int type,
 		u8 fault_reason, u32 pasid, u16 source_id,
 		unsigned long long addr)

include/linux/dmar.h

···
 struct irq_data;
 extern void dmar_msi_unmask(struct irq_data *data);
 extern void dmar_msi_mask(struct irq_data *data);
-extern void dmar_msi_read(int irq, struct msi_msg *msg);
 extern void dmar_msi_write(int irq, struct msi_msg *msg);
 extern int dmar_set_interrupt(struct intel_iommu *iommu);
 extern irqreturn_t dmar_fault(int irq, void *dev_id);