drm/exynos: exynos5433_decon: fix wrong state assignment in decon_enable

Patch ebf3fd40 ("drm/exynos: add
pm_runtime to DECON 5433") removed some code from decon_enable()
function, but it left set_bit(BIT_SUSPENDED, &ctx->flags) call, which
was earlier called only in error path. This patch removes it, what
finally lets driver to go out of suspended state.

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