drm/exynos: fix wrong pipe calculation for crtc

We get wrong pipe value for crtc since commit 93bca243 ("drm/exynos:
remove struct exynos_drm_manager"). We should should increase pipe value
before call exynos_drm_crtc_create.

Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>