egl: directly access static members instead of using _egl{Get,Set}ConfigKey()

This function is meant for when the attribute is unknown at compile-time
(eg. user-specified), but in all these cases it is much simpler to just
read/write the member directly.

Suggested-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Tested-by: Marge Bot <mesa/mesa!3816>
Part-of: <mesa/mesa!3816>
40 jobs for !3816 with egl-direct-deref in 20 minutes and 46 seconds (queued for 3 seconds)
merge request