drm/i915/switcheroo: use struct drm_device based logging

Convert all the pr_* logging macros to the struct drm_device based
macros to provide device specific logging.

No functional changes.

Cc: Wambui Karuga <wambui.karugax@gmail.com>
Reviewed-by: NWambui Karuga <wambui.karugax@gmail.com>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200402114819.17232-9-jani.nikula@intel.com

drivers/gpu/drm/i915/i915_switcheroo.c

@@ -20,14 +20,14 @@ static void i915_switcheroo_set_state(struct pci_dev *pdev,
 	}
 
 	if (state == VGA_SWITCHEROO_ON) {
-		pr_info("switched on\n");
+		drm_info(&i915->drm, "switched on\n");
 		i915->drm.switch_power_state = DRM_SWITCH_POWER_CHANGING;
 		/* i915 resume handler doesn't set to D0 */
 		pci_set_power_state(pdev, PCI_D0);
 		i915_resume_switcheroo(i915);
 		i915->drm.switch_power_state = DRM_SWITCH_POWER_ON;
 	} else {
-		pr_info("switched off\n");
+		drm_info(&i915->drm, "switched off\n");
 		i915->drm.switch_power_state = DRM_SWITCH_POWER_CHANGING;
 		i915_suspend_switcheroo(i915, pmm);
 		i915->drm.switch_power_state = DRM_SWITCH_POWER_OFF;