Fixed warning C4245: 'initializing': conversion from 'int' to 'Uint32', signed/unsigned mismatch

test/testautomation_intrinsics.c

@@ -251,7 +251,7 @@ SDL_TARGETING("sse4.1") static void kernel_ints_mul_sse4_1(Sint32 *dest, const S
 
 #ifdef SDL_SSE4_2_INTRINSICS
 SDL_TARGETING("sse4.2") static Uint32 calculate_crc32c_sse4_2(const char *text) {
-    Uint32 crc32c = ~0;
+    Uint32 crc32c = ~0u;
     size_t len = SDL_strlen(text);
 
 #if defined(__x86_64__) || defined(_M_X64)