sh4: add required #include, fix build

Signed-off-by: Mans Rullgard <mans@mansr.com>

libavcodec/sh4/qpel.c

@@ -21,6 +21,8 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+#include "libavutil/common.h"
+
 #define PIXOP2(OPNAME, OP) \
 \
 static inline void OPNAME ## _pixels4_l2_aligned(uint8_t *dst, const uint8_t *src1, const uint8_t *src2, int dst_stride, int src_stride1, int src_stride2, int h) \