Fix enum order for backwards compatibility

The new enum member introduced in 2a164e968 broke ABI with previous
versions of vk_icd.h, resulting in a segfault on latest mesa (which does
not yet have this commit in their vendored copy of vk_icd.h, thus
breaking the order of enum members).

include/vulkan/vk_icd.h

@@ -85,13 +85,13 @@ typedef enum {
     VK_ICD_WSI_PLATFORM_WIN32,
     VK_ICD_WSI_PLATFORM_XCB,
     VK_ICD_WSI_PLATFORM_XLIB,
-    VK_ICD_WSI_PLATFORM_DIRECTFB,
     VK_ICD_WSI_PLATFORM_ANDROID,
     VK_ICD_WSI_PLATFORM_MACOS,
     VK_ICD_WSI_PLATFORM_IOS,
     VK_ICD_WSI_PLATFORM_DISPLAY,
     VK_ICD_WSI_PLATFORM_HEADLESS,
     VK_ICD_WSI_PLATFORM_METAL,
+    VK_ICD_WSI_PLATFORM_DIRECTFB,
 } VkIcdWsiPlatform;
 
 typedef struct {