Fix circular --config for SDL port.

When using the command line options, we had a circular issue:
- using `LoadConfig()` before `ReadOpts()` would mean the `--config` is
ignored.
- using `ReadOpts()` before `LoadConfig()` would mean the command line
options were ignored in favor of the default ones.

If we want to use a custom `vbam.ini`, we need to load it with
`--config`. Now we only consider params order on command line.

src/common/ConfigManager.cpp

@@ -898,6 +898,7 @@ int ReadOpts(int argc, char ** argv)
 			preferences = NULL;
 			OpenPreferences(optarg);
 			fclose(f);
+			LoadConfig();
 		}
 		break;
 		case 'd':

src/sdl/SDL.cpp

@@ -1538,8 +1538,8 @@ int main(int argc, char** argv)
     gb_effects_config.surround = false;
     gb_effects_config.enabled = false;
 
-    ReadOpts(argc, argv);
     LoadConfig(); // Parse command line arguments (overrides ini)
+    ReadOpts(argc, argv);
 
     inputSetKeymap(PAD_1, KEY_LEFT, ReadPrefHex("Joy0_Left"));
     inputSetKeymap(PAD_1, KEY_RIGHT, ReadPrefHex("Joy0_Right"));