exynos: change the license to X11/MIT

Change GPL license of Exynos related code to X11/MIT.

I'd like to keep a consistent license across all Exynos code
because License checker notices two more licenses exist
in libdrm.

For the license change I need to get your agree - all committers.
So please give me Acked-by if you agree with me.

Signed-off-by: Inki Dae <inki.dae@samsung.com>
Acked-by: Hyungwon Hwang <human.hwang@samsung.com>
Acked-by: SooChan Lim <sc1.lim@samsung.com>
Acked-by: Sangjin LEE <lsj119@samsung.com>
Acked-by: Boram Park <boram1288.park@samsung.com>
Acked-by: Seung-Woo Kim <sw0312.kim@samsung.com>
Acked-by: Joonyoung Shim <jy0922.shim@samsung.com>
Acked-by: Emil Velikov <emil.l.velikov@gmail.com>
Acked-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
Acked-by: Jan Vesely <jan.vesely@rutgers.edu>