drm/msm/sde: update vblank and underrun isr handling

Current sde driver enables the underrun interrupt for
all interfaces during bootup. That's not a desired
behavior. It should be handled through each interface
when it is enabled/disabled. This patch updates the
irq APIs on each interface to handle generic irq request
and uses them for vblank, underrun, etc interrupts.

Change-Id: I890110eef975555a771a0690c5f762b0a3f18737
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>