drm/exynos/decon5433: kill BIT_SUSPENDED flag

Exynos tracked suspend state to prevent touching disabled HW. After
fixing disable order in HDMI and moving TE handling to DECON it is
not needed anymore - all IRQ handlers and callbacks touching HW
are called only with enabled DECON.

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>