drm/xe: clear the serviced bits on INTR_IDENTITY_REG

The spec for this register, like many other interrupt related ones,
asks software to write back '1' to clear the serviced bits. Let's
respect the spec.

v2:
- Update commit message
- Add missing CC

Signed-off-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
CC: Daniele Spurio Ceraolo <daniele.ceraolospurio@intel.com>
CC: Lucas De Marchi <lucas.demarchi@intel.com>
CC: Rodrigo Vivi <rodrigo.vivi@intel.com>
CC: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/xe/xe_irq.c

@@ -231,7 +231,7 @@ gt_engine_identity(struct xe_device *xe,
 		return 0;
 	}
 
-	xe_mmio_write32(mmio, INTR_IDENTITY_REG(bank), INTR_DATA_VALID);
+	xe_mmio_write32(mmio, INTR_IDENTITY_REG(bank), ident);
 
 	return ident;
 }