egl: rename _eglMatchDriver() to _eglInitializeDisplay()

... and fix the comment to better reflect what this really does.

The whole "match a driver at runtime" thing has been gone for years.

Signed-off-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Marcin Ślusarz <marcin.slusarz@intel.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6037>