iommu: arm-smmu: improve tlbsync timeout debugging

Call BUG() right after the first TLB sync timeout which will helps in
getting the system state information at that point of time that further
helps in debugging.

Change-Id: Id2d3eb491080b12486c99966da72afe2f6deefb4
Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>