drm/i915: Use expcitly fixed type in compat32 structs

I was confused shortly whether the compat was needed for the int,
until I noticed the pointer in the original.

Also remove typedef.

v2: Review from Chris.
- Add comments.
- Also change the int param in the original structure.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

include/uapi/drm/i915_drm.h

@@ -358,7 +358,11 @@ typedef struct drm_i915_irq_wait {
 #define I915_PARAM_HAS_RESOURCE_STREAMER 36
 
 typedef struct drm_i915_getparam {
-	int param;
+	s32 param;
+	/*
+	 * WARNING: Using pointers instead of fixed-size u64 means we need to write
+	 * compat32 code. Don't repeat this mistake.
+	 */
 	int __user *value;
 } drm_i915_getparam_t;