util: Import a copy of drm's libsync.h

libsync.h is one of the common dependencies on libdrm from drivers that
otherwise don't want libdrm.  Given that it's header-only code, just
import it to Mesa instead of forcing library dependencies on our users.

Copied from libdrm commit a84caff71be9 (" intel: Add PCI ID support to RKL
platform")

Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6821>
1 file changed