mips: Move MMI function declarations to a header.

This fixes compilation with -Werror=missing-prototypes.

libavcodec/ps2/dsputil_mmi.c

@@ -25,10 +25,6 @@
 #include "libavcodec/dsputil.h"
 #include "mmi.h"
 
-void ff_mmi_idct_put(uint8_t *dest, int line_size, DCTELEM *block);
-void ff_mmi_idct_add(uint8_t *dest, int line_size, DCTELEM *block);
-void ff_mmi_idct(DCTELEM *block);
-
 static void clear_blocks_mmi(DCTELEM * blocks)
 {
         __asm__ volatile(

libavcodec/ps2/mmi.h

@@ -21,6 +21,14 @@
 #ifndef AVCODEC_PS2_MMI_H
 #define AVCODEC_PS2_MMI_H
 
+#include <stdint.h>
+
+#include "libavcodec/dsputil.h"
+
+void ff_mmi_idct_put(uint8_t *dest, int line_size, DCTELEM *block);
+void ff_mmi_idct_add(uint8_t *dest, int line_size, DCTELEM *block);
+void ff_mmi_idct(DCTELEM *block);
+
 #define align16 __attribute__ ((aligned (16)))
 
 /*