ACPI: scan: Constify acpi_dma_supported() helper function

Constify arguments to acpi_dma_supported(). The function doesn't need
to change the content of the passed argument and when it's const it
allows to supply the result of other functions that may return a pointer
to a constant object.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
[ rjw: Subject edit ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/scan.c

@@ -1404,7 +1404,7 @@ void acpi_free_pnp_ids(struct acpi_device_pnp *pnp)
  *
  * Return false if DMA is not supported. Otherwise, return true
  */
-bool acpi_dma_supported(struct acpi_device *adev)
+bool acpi_dma_supported(const struct acpi_device *adev)
 {
 	if (!adev)
 		return false;

include/acpi/acpi_bus.h

@@ -586,7 +586,7 @@ struct acpi_pci_root {
 
 /* helper */
 
-bool acpi_dma_supported(struct acpi_device *adev);
+bool acpi_dma_supported(const struct acpi_device *adev);
 enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev);
 int acpi_dma_get_range(struct device *dev, u64 *dma_addr, u64 *offset,
 		       u64 *size);

include/linux/acpi.h

@@ -911,7 +911,7 @@ acpi_create_platform_device(struct acpi_device *adev,
 	return NULL;
 }
 
-static inline bool acpi_dma_supported(struct acpi_device *adev)
+static inline bool acpi_dma_supported(const struct acpi_device *adev)
 {
 	return false;
 }