mir: Disable Mir by default as Mir supports Wayland clients

Also remove enabling VK support for Mir

configure.in

@@ -1468,8 +1468,8 @@ dnl Check for Mir
 CheckMir()
 {
     AC_ARG_ENABLE(video-mir,
-AC_HELP_STRING([--enable-video-mir], [use Mir video driver [[default=yes]]]),
-                  ,enable_video_mir=yes)
+AC_HELP_STRING([--enable-video-mir], [use Mir video driver [[default=no]]]),
+                  ,enable_video_mir=no)
 
     if test x$enable_video = xyes -a x$enable_video_mir = xyes; then
         AC_PATH_PROG(PKG_CONFIG, pkg-config, no)

src/video/SDL_vulkan_internal.h

@@ -38,9 +38,6 @@
 #if SDL_VIDEO_DRIVER_COCOA
 #define VK_USE_PLATFORM_MACOS_MVK
 #endif
-#if SDL_VIDEO_DRIVER_MIR
-#define VK_USE_PLATFORM_MIR_KHR
-#endif
 #if SDL_VIDEO_DRIVER_UIKIT
 #define VK_USE_PLATFORM_IOS_MVK
 #endif