drm/exynos: fimd: check whether exynos_drm_crtc_create succeed or not

>From the commit "drm/exynos: fix the execution order in FIMD
initialization" (598285bfdce46d7c47632a2ba4b980f60be4a677), the error
checking code is removed improperly. This patch fix the regression.

Signed-off-by: Hyungwon Hwang <human.hwang@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>