jpeg2000: merge mant type from j2k

mant fits in 16bit
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/jpeg2000.h

@@ -144,7 +144,7 @@ typedef struct Jpeg2000CodingStyle {
 
 typedef struct Jpeg2000QuantStyle {
     uint8_t expn[32 * 3];  // quantization exponent
-    uint32_t mant[32 * 3]; // quantization mantissa
+    uint16_t mant[32 * 3]; // quantization mantissa
     uint8_t quantsty;      // quantization style
     uint8_t nguardbits;    // number of guard bits
 } Jpeg2000QuantStyle;