drm/msm/sde: Initialize the mmu contexts early during probe

Reg dma block will allocate the memory during the probe for supported
features. Sde mmu context banks should be initialized before the reg dma
init is called. Change moves the smmu init to the start of the probe.

Change-Id: Id38db251afdb855339e8d5a4bcb9e3464bbe7ae2
Signed-off-by: Gopikrishnaiah Anandan <agopik@codeaurora.org>