omap iommu: add functionality to get TLB miss interrupt

In order to enable TLB miss interrupt, the TWL should be
disabled. This patch provides the functionality to get the
MMU fault interrupt for a TLB miss in the cases where the
users are working with the locked TLB entries and with TWL
disabled.
New interface is added to select twl and to enable TLB miss
interrupt.

Signed-off-by: Hari Kanigeri <h-kanigeri2@ti.com>
Signed-off-by: Ramesh Gupta <grgupta@ti.com>
Signed-off-by: Hiroshi Doyu <Hiroshi.DOYU@nokia.com>