buffer: make enum wlr_buffer_cap public

Custom backends and renderers need to implement
wlr_backend_impl.get_buffer_caps and
wlr_renderer_impl.get_render_buffer_caps. They can't if enum
wlr_buffer_cap isn't made public.

(cherry picked from commit a38baec1f8)

backend/drm/backend.c

@@ -13,7 +13,6 @@
 #include <wlr/util/log.h>
 #include <xf86drm.h>
 #include "backend/drm/drm.h"
-#include "types/wlr_buffer.h"
 #include "util/signal.h"
 
 struct wlr_drm_backend *get_drm_backend_from_backend(

backend/drm/drm.c

@@ -28,7 +28,6 @@
 #include "render/drm_format_set.h"
 #include "render/swapchain.h"
 #include "render/wlr_renderer.h"
-#include "types/wlr_buffer.h"
 #include "util/signal.h"
 
 static const uint32_t SUPPORTED_OUTPUT_STATE =

backend/headless/backend.c

@@ -14,7 +14,6 @@
 #include "render/drm_format_set.h"
 #include "render/gbm_allocator.h"
 #include "render/wlr_renderer.h"
-#include "types/wlr_buffer.h"
 #include "util/signal.h"
 
 struct wlr_headless_backend *headless_backend_from_backend(

backend/wayland/backend.c

@@ -21,7 +21,6 @@
 #include "render/drm_format_set.h"
 #include "render/pixel_format.h"
 #include "render/wlr_renderer.h"
-#include "types/wlr_buffer.h"
 #include "util/signal.h"
 
 #include "drm-client-protocol.h"

backend/wayland/output.c

@@ -19,7 +19,6 @@
 #include "render/pixel_format.h"
 #include "render/swapchain.h"
 #include "render/wlr_renderer.h"
-#include "types/wlr_buffer.h"
 #include "util/signal.h"
 
 #include "linux-dmabuf-unstable-v1-client-protocol.h"

backend/x11/backend.c

@@ -33,7 +33,6 @@
 #include "backend/x11.h"
 #include "render/allocator.h"
 #include "render/drm_format_set.h"
-#include "types/wlr_buffer.h"
 #include "util/signal.h"
 
 // See dri2_format_for_depth in mesa

backend/x11/output.c

@@ -21,7 +21,6 @@
 #include <wlr/util/log.h>
 
 #include "backend/x11.h"
-#include "types/wlr_buffer.h"
 #include "util/signal.h"
 #include "util/time.h"