msm: camera: custom: Add support for SW sync & snapshot

Add support to handle SW sync & ZSLSnapshot. Add substate machine
and mechanism to handle the lifecycle of requests based on irqs
accordingly.

CRs-Fixed: 2524308
Change-Id: Ie5ba97d4ae1b38f4b44c2d3935d2882df59fcac6
Signed-off-by: Karthik Anantha Ram <kartanan@codeaurora.org>