SDL_hidapi_steam.c: Fix compilation under c2x.

When N2935 is implemented, the enum breaks compilation. Use a #define of
the SDL booleans instead.

(cherry picked from commit 975039ce0d3587c42e11f2922240957fc8f74166)

src/joystick/hidapi/SDL_hidapi_steam.c

@@ -35,11 +35,9 @@
 
 #include <stdint.h>
 
-typedef enum
+#define bool SDL_bool
-{
+#define true SDL_TRUE
-    false,
+#define false SDL_FALSE
-    true
-} bool;
 
 typedef uint32_t uint32;
 typedef uint64_t uint64;