Revert "libavutil: Use an intermediate variable in AV_COPY*U"

This reverts commit 014773b6.

Since 230b1c07, the bytewise AV_W*() macros only expand their
argument once, i.e. doing exactly the same change as was done
in the AV_COPY*U macros, so this change is no longer necessary.
Signed-off-by: Martin Storsjö <martin@martin.st>

libavutil/intreadwrite.h

@@ -478,11 +478,7 @@ union unaligned_16 { uint16_t l; } __attribute__((packed)) av_alias;
  * memory locations.
  */
 
-#define AV_COPYU(n, d, s)                                       \
-    do {                                                        \
-        uint##n##_t val = AV_RN##n(s);                          \
-        AV_WN##n(d, val);                                       \
-    } while (0)
+#define AV_COPYU(n, d, s) AV_WN##n(d, AV_RN##n(s));
 
 #ifndef AV_COPY16U
 #   define AV_COPY16U(d, s) AV_COPYU(16, d, s)