drm/i915: Drop unnecessary #include <linux/vga_switcheroo.h>

Commit 599bbb9d ("drm/i915: i915 cannot provide switcher services.")
removed all remaining vga_switcheroo symbols from intel_acpi.c but left
the include. Drop it.
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_acpi.c

@@ -5,7 +5,6 @@
  */
 #include <linux/pci.h>
 #include <linux/acpi.h>
-#include <linux/vga_switcheroo.h>
 #include <drm/drmP.h>
 #include "i915_drv.h"