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: I87693c83f19e0dc013c81d89bd9f03207fde2d69
Signed-off-by: Akash Asthana <akashast@codeaurora.org>