BIT_IRQS_ENABLED was never set because of incorrect test in
decon_vlank_enable() function, what resulted in lack of enabling vblank
support. This patch fixes this issue.
Signed-off-by: NMarek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: NInki Dae <inki.dae@samsung.com>