drm/i915: rename intel_fb.c to intel_fbdev.c

This file is all about the legacy fbdev support. If we want to extract
framebuffer functions, we better put those into a separate file.

Also rename functions accordingly, only two have used the intel_fb_
prefix anyway.

Reviewed-by: Chon Ming Lee <chon.ming.lee@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 53c958c..42cddc1 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1853,7 +1853,7 @@
 		return;
 
 	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
-		intel_fb_restore_mode(dev);
+		intel_fbdev_restore_mode(dev);
 		vga_switcheroo_process_delayed_switch();
 		return;
 	}