media: staging/intel-ipu3: mark PM function as __maybe_unused

BugLink: https://bugs.launchpad.net/bugs/1837517

[ Upstream commit 948dff7 ]

The imgu_rpm_dummy_cb() looks like an API misuse that is explained
in the comment above it. Aside from that, it also causes a warning
when power management support is disabled:

drivers/staging/media/ipu3/ipu3.c:794:12: error: 'imgu_rpm_dummy_cb' defined but not used [-Werror=unused-function]

The warning is at least easy to fix by marking the function as
__maybe_unused.

Fixes: 7fc7af6 ("media: staging/intel-ipu3: Add imgu top level pci device driver")

Signed-off-by: Arnd Bergmann <[email protected]>
Signed-off-by: Sakari Ailus <[email protected]>
Signed-off-by: Mauro Carvalho Chehab <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
Signed-off-by: Khalid Elmously <[email protected]>
Signed-off-by: Stefan Bader <[email protected]>

drivers/staging/media/ipu3/ipu3.c

@@ -792,7 +792,7 @@ static int __maybe_unused imgu_resume(struct device *dev)
  * PCI rpm framework checks the existence of driver rpm callbacks.
  * Place a dummy callback here to avoid rpm going into error state.
  */
-static int imgu_rpm_dummy_cb(struct device *dev)
+static __maybe_unused int imgu_rpm_dummy_cb(struct device *dev)
 {
 	return 0;
 }