turnip: Use Mesa's libsync.h instead of libdrm's libsync.h.

Given that we already link to Android's libsync, use it instead of using a
build-time dependency on libdrm for the KGSL path.  This also would help
for older kernel compat with KGSL.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6821>

src/freedreno/vulkan/tu_android.c

@@ -37,6 +37,7 @@
 
 #include "drm-uapi/drm_fourcc.h"
 
+#include "util/libsync.h"
 #include "util/os_file.h"
 
 static int

src/freedreno/vulkan/tu_device.c

@@ -28,7 +28,7 @@
 #include "tu_private.h"
 
 #include <fcntl.h>
-#include <libsync.h>
+#include <poll.h>
 #include <stdbool.h>
 #include <string.h>
 #include <sys/sysinfo.h>