egl: fix zink init
What does this MR do and why?
egl: fix zink init
* close(fd) requires also resetting the fd=-1 or else boom
* checking driver_name is broken because loader_get_driver_for_fd()
uses MESA_LOADER_DRIVER_OVERRIDE, so there's no way to differentiate
an inferred load
Fixes: b907eb47504 ("egl: don't bind zink under dri2/3")