drm/exynos: MAINTAINERS: move Joonyoung Shim to credits

Emails to Joonyoung Shim bounce ("550 5.1.1 Recipient address rejected:
User unknown"), so move him to credits file.
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

CREDITS

@@ -3491,6 +3491,10 @@ D: wd33c93 SCSI driver (linux-m68k)
 S: San Jose, California
 S: USA
 
+N: Joonyoung Shim
+E: y0922.shim@samsung.com
+D: Samsung Exynos DRM drivers
+
 N: Robert Siemer
 E: Robert.Siemer@gmx.de
 P: 2048/C99A4289 2F DC 17 2E 56 62 01 C8  3D F2 AC 09 F2 E5 DD EE

MAINTAINERS

@@ -6656,7 +6656,6 @@ F:	drivers/gpu/drm/bridge/
 
 DRM DRIVERS FOR EXYNOS
 M:	Inki Dae <inki.dae@samsung.com>
-M:	Joonyoung Shim <jy0922.shim@samsung.com>
 M:	Seung-Woo Kim <sw0312.kim@samsung.com>
 M:	Kyungmin Park <kyungmin.park@samsung.com>
 L:	dri-devel@lists.freedesktop.org