device: acpi_name() should take a const struct device

There's no reason to mutate the struct device when determining
the ACPI name for a device. Adjust the function pointer
signature and the respective implementations to use const
struct device.

Change-Id: If5e1f4de36a53646616581b01f47c4e86822c42e
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/21527
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Subrata Banik <subrata.banik@intel.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/northbridge/intel/sandybridge/gma.c

@@ -718,7 +718,7 @@ gma_write_acpi_tables(struct device *const dev,
 	return current;
 }
 
-static const char *gma_acpi_name(device_t dev)
+static const char *gma_acpi_name(const struct device *dev)
 {
 	return "GFX0";
 }