[PATCH -next] drm/i915: Add missing include file <linux/math64.h>

[YueHaibing]

Fix build error:
./drivers/gpu/drm/i915/selftests/i915_random.h: In function i915_prandom_u32_max_state:
./drivers/gpu/drm/i915/selftests/i915_random.h:48:23: error:
 implicit declaration of function mul_u32_u32; did you mean mul_u64_u32_div? [-Werror=implicit-function-declaration]
  return upper_32_bits(mul_u32_u32(prandom_u32_state(state), ep_ro));

Reported-by: Hulk Robot <hulkci at huawei.com>
Fixes: 7ce5b6850b47 ("drm/i915/selftests: Use mul_u32_u32() for 32b x 32b -> 64b result")
Signed-off-by: YueHaibing <yuehaibing at huawei.com>
---
 drivers/gpu/drm/i915/selftests/i915_random.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/i915/selftests/i915_random.h b/drivers/gpu/drm/i915/selftests/i915_random.h
index 35cc69a..f650cfb 100644
--- a/drivers/gpu/drm/i915/selftests/i915_random.h
+++ b/drivers/gpu/drm/i915/selftests/i915_random.h
@@ -26,6 +26,7 @@
 #define __I915_SELFTESTS_RANDOM_H__
 
 #include <linux/random.h>
+#include <linux/math64.h>
 
 #include "../i915_selftest.h"
 
-- 
2.7.4