video: Make the rest of the FIFO variables atomic

src/video/vid_ati_mach64.c

@@ -22,6 +22,7 @@
 #include <string.h>
 #include <stdlib.h>
 #include <wchar.h>
+#include <stdatomic.h>
 #define HAVE_STDARG_H
 #include <86box/86box.h>
 #include <86box/device.h>
@@ -215,7 +216,7 @@ typedef struct mach64_t {
     } accel;
 
     fifo_entry_t fifo[FIFO_SIZE];
-    volatile int fifo_read_idx, fifo_write_idx;
+    atomic_int fifo_read_idx, fifo_write_idx;
 
     thread_t *fifo_thread;
     event_t  *wake_fifo_thread;

src/video/vid_mga.c

@@ -18,6 +18,7 @@
 #include <string.h>
 #include <stdlib.h>
 #include <wchar.h>
+#include <stdatomic.h>
 #include <86box/86box.h>
 #include <86box/io.h>
 #include <86box/timer.h>
@@ -429,7 +430,7 @@ typedef struct mystique_t {
         xzoomctrl,
         pixel_count, trap_count;
 
-    volatile int busy, blitter_submit_refcount,
+    atomic_int busy, blitter_submit_refcount,
         blitter_submit_dma_refcount, blitter_complete_refcount,
         endprdmasts_pending, softrap_pending,
         fifo_read_idx, fifo_write_idx;

src/video/vid_s3.c

@@ -22,6 +22,7 @@
 #include <stdlib.h>
 #include <math.h>
 #include <wchar.h>
+#include <stdatomic.h>
 #include <86box/86box.h>
 #include <86box/device.h>
 #include <86box/io.h>
@@ -298,7 +299,7 @@ typedef struct s3_t {
         int          input;
         int          len, start;
         int          odf, idf, yuv;
-        volatile int busy;
+        atomic_int busy;
     } videoengine;
 
     struct
@@ -334,7 +335,7 @@ typedef struct s3_t {
     } streams;
 
     fifo_entry_t fifo[FIFO_SIZE];
-    volatile int fifo_read_idx, fifo_write_idx;
+    atomic_int   fifo_read_idx, fifo_write_idx;
 
     uint8_t fifo_thread_run;
 
@@ -351,10 +352,10 @@ typedef struct s3_t {
     uint32_t hwc_fg_col, hwc_bg_col;
     int      hwc_col_stack_pos;
 
-    int          translate;
-    int          enable_8514;
-    int          color_16bit;
-    volatile int busy, force_busy;
+    int        translate;
+    int        enable_8514;
+    int        color_16bit;
+    atomic_int busy, force_busy;
 
     uint8_t thread_run, serialport;
     void   *i2c, *ddc;