iommu/omap: add logic to save/restore locked TLBs

The MMUs provide a mechanism to lock TLB entries to avoid
eviction and fetching of frequently used page table entries.
These TLBs lose context when the MMUs are turned OFF. Add the
logic to save and restore these locked TLBS during suspend
and resume respectively. There are no locked TLBs during
initial power ON, and they need not be saved during final
shutdown.

Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>