i2c: nvidia-gpu: drop empty stub for runtime pm

After the commit c5eb119 ("PCI / PM: Allow runtime PM without callback
functions") we no more need empty stubs for runtime-pm to work.

The driver has no device specific task(s) for .suspend() . The stub was
placed just for runtime-pm, which can be dropped now.

Reported-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Vaibhav Gupta <vaibhavgupta40@gmail.com>
Reviewed-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

drivers/i2c/busses/i2c-nvidia-gpu.c

@@ -353,15 +353,7 @@ static void gpu_i2c_remove(struct pci_dev *pdev)
 	pci_free_irq_vectors(pdev);
 }
 
-/*
- * We need gpu_i2c_suspend() even if it is stub, for runtime pm to work
- * correctly. Without it, lspci shows runtime pm status as "D0" for the card.
- * Documentation/power/pci.rst also insists for driver to provide this.
- */
-static __maybe_unused int gpu_i2c_suspend(struct device *dev)
-{
-	return 0;
-}
+#define gpu_i2c_suspend NULL
 
 static __maybe_unused int gpu_i2c_resume(struct device *dev)
 {