Drop wl_drm again

In [1] we re-introduced a debug flag to enable wl_drm. Time has
passed and Xwayland + VA-API + amdvlk now all support
linux-dmabuf-v1.

[1]: #7916

Author: emersion

include/sway/server.h

@@ -145,7 +145,6 @@ struct sway_debug {
 	bool noatomic;         // Ignore atomic layout updates
 	bool txn_timings;      // Log verbose messages about transactions
 	bool txn_wait;         // Always wait for the timeout before applying
-	bool legacy_wl_drm;    // Enable the legacy wl_drm interface
 };
 
 extern struct sway_debug debug;

sway/main.c

@@ -161,8 +161,6 @@ void enable_debug_flag(const char *flag) {
 		debug.txn_timings = true;
 	} else if (strncmp(flag, "txn-timeout=", 12) == 0) {
 		server.txn_timeout_ms = atoi(&flag[12]);
-	} else if (strcmp(flag, "legacy-wl-drm") == 0) {
-		debug.legacy_wl_drm = true;
 	} else {
 		sway_log(SWAY_ERROR, "Unknown debug flag: %s", flag);
 	}

sway/server.c

@@ -244,9 +244,6 @@ bool server_init(struct sway_server *server) {
 	if (wlr_renderer_get_texture_formats(server->renderer, WLR_BUFFER_CAP_DMABUF) != NULL) {
 		server->linux_dmabuf_v1 = wlr_linux_dmabuf_v1_create_with_renderer(
 			server->wl_display, 4, server->renderer);
-		if (debug.legacy_wl_drm) {
-			wlr_drm_create(server->wl_display, server->renderer);
-		}
 	}
 
 	server->allocator = wlr_allocator_autocreate(server->backend,