qcom-geni-se: Handle return value from iommu_map_and_attach function

There seems an issue of not handling failures from
geni_se_iommu_map_and_attach(). This change takes care
of returning value appropriately to the caller.

Change-Id: I4e2d580f7fe5cad85ab7f740dc50a6dba3046bf3
Signed-off-by: Akash Asthana <akashast@codeaurora.org>