avcodec/kmvc: Move commonly used variables to the front of the context

Reduces codesize because the offset in pointer+offset addressing
requires less bytes to encode. Reduces the size of .text from 8871B
to 8146B (GCC 10, -O3, x64).

Reviewed-by: Tomas Härdin <tjoppen@acc.umu.se>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

libavcodec/kmvc.c

@@ -44,12 +44,12 @@
 typedef struct KmvcContext {
     AVCodecContext *avctx;
 
+    GetByteContext g;
+    uint8_t *cur, *prev;
     int setpal;
     int palsize;
     uint32_t pal[MAX_PALSIZE];
-    uint8_t *cur, *prev;
     uint8_t frm0[320 * 200], frm1[320 * 200];
-    GetByteContext g;
 } KmvcContext;
 
 typedef struct BitBuf {