avutil/mips: Avoid instruction exception caused by gssqc1/gslqc1.

Ensure the address accesed by gssqc1/gslqc1 are 16-byte aligned.

libavcodec/mips/simple_idct_mmi.c

@@ -39,7 +39,7 @@
 #define COL_SHIFT 20
 #define DC_SHIFT 3
 
-DECLARE_ALIGNED(8, const int16_t, W_arr)[46] = {
+DECLARE_ALIGNED(16, const int16_t, W_arr)[46] = {
     W4,  W2,  W4,  W6,
     W1,  W3,  W5,  W7,
     W4,  W6, -W4, -W2,

libavutil/mips/mmiutils.h

@@ -205,7 +205,7 @@
  * backup register
  */
 #define BACKUP_REG \
-  double temp_backup_reg[8];                                    \
+  LOCAL_ALIGNED_16(double, temp_backup_reg, [8]);               \
   if (_MIPS_SIM == _ABI64)                                      \
     __asm__ volatile (                                          \
       "gssqc1       $f25,      $f24,       0x00(%[temp])  \n\t" \