exynos_drm: Clean up duplicated assignment in exynos_drm_driver

num_ioctls is already assigned when declaring the exynos_drm_driver
structure.  No need to duplicate it here.

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.co.uk>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>