drm/i915: cleanup a min_t() cast

The lower layers of sysfs will not allow an "offset" of more than
GEN7_L3LOG_SIZE and also l3_access_valid() caps it a second time.  But
it's a little easier to audit if we don't have to worry that the
subtraction will result in negative values.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_sysfs.c

@@ -131,7 +131,7 @@ i915_l3_read(struct file *filp, struct kobject *kobj,
 	if (ret)
 		return ret;
 
-	count = min_t(int, GEN7_L3LOG_SIZE-offset, count);
+	count = min_t(size_t, GEN7_L3LOG_SIZE - offset, count);
 
 	ret = i915_mutex_lock_interruptible(drm_dev);
 	if (ret)