drm/i915: Fixup stub definitions for intel_opregion_suspend|resume

248 "multiple definition of ...". E.g.:

LD [M] drivers/gpu/drm/i915/i915.o
ld: drivers/gpu/drm/i915/i915_irq.o: in function `intel_opregion_resume':
i915_irq.c:(.text+0x58f0): multiple definition of `intel_opregion_resume';
drivers/gpu/drm/i915/i915_drv.o:i915_drv.c:(.text+0x2d40): first defined here

Reported-by: Randy Dunlap <[e-mail]>
Reported-by: Stephen Rothwell <[e-mail]>
Fixes: a950adc6c343 ("drm/i915: Stop calling intel_opregion unregister/register in suspend/resume")
Signed-off-by: Chris Wilson <[e-mail]>
Acked-by: Randy Dunlap <[e-mail]> # build tested
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/i915/intel_opregion.h

···
 {
 }
 
-void intel_opregion_resume(struct drm_i915_private *dev_priv)
+static inline void intel_opregion_resume(struct drm_i915_private *dev_priv)
 {
 }
 
-void intel_opregion_suspend(struct drm_i915_private *dev_priv,
-			    pci_power_t state)
+static inline void intel_opregion_suspend(struct drm_i915_private *dev_priv,
+					  pci_power_t state)
 {
 }