coresight: tmc: clear has_iommu flag when smmu is bypassed

When SMMU works in bypass mode, set has_iommu to false.  ETR
can use SG mode.

Change-Id: Ic7a6814cace92098473e4b5302408034e662058d
Signed-off-by: Tingwei Zhang <tingwei@codeaurora.org>