drm/exynos: rotator: Fix DRM_MODE_REFLECT_{X,Y} interpretation

Horizontal (DRM_MODE_REFLECT_Y) and vertical (DMR_MODE_REFLECT_Y) flip
were swapped in Rotator driver. Fix this by swapping code for interpreting
them.

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