drm/msm/sde: Add LTM interrupts into irq framework

LTM HW block is newly introduced in Kona family, this change
adds the LTM related HW interrupts into the irq framework.

Change-Id: Ieba5b102fcec8adaf57f58919ab47ec492f50f3e
Signed-off-by: Ping Li <pingli@codeaurora.org>