drm/exynos: Drop useless check from exynos_drm_{suspend,resume}

The virtual Exynos DRM device has no runtime PM enabled, so checking
for its runtime suspended state is useless.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>