MAINTAINERS: update maintainer entry for Exynos DP driver

Recently, Exynos DP driver was moved from drivers/video/exynos/
directory to drivers/gpu/drm/exynos/ directory. So, I update
and add maintainer entry for Exynos DP driver.

Signed-off-by: Jingoo Han <[e-mail]>
Signed-off-by: Inki Dae <[e-mail]>
Signed-off-by: Dave Airlie <[e-mail]>

MAINTAINERS

···
 F:	drivers/extcon/
 F:	Documentation/extcon/
 
+EXYNOS DP DRIVER
+M:	Jingoo Han <[e-mail]>
+L:	[e-mail]
+S:	Maintained
+F:	drivers/gpu/drm/exynos/exynos_dp*
+
 EXYNOS MIPI DISPLAY DRIVERS
 M:	Inki Dae <[e-mail]>
 M:	Donghwa Lee <[e-mail]>