msm: sde: Reset the iommu_attached flag after detach

When the secure camera starts, we detach the secure CB. We don't
reset the iommu_attached flag to avoid iommu attach during the
secure session. The improper flag value is causing imbalance in
the clock voting, and is causing crashes when secure camera use
cases are run back to back with device suspend/resume.

The sde_smmu_attach function already takes care of avoiding attach
during secure session. So, we can reset the flag to avoid imbalance
in the clock voting.

Change-Id: Ie57e930031800a0edc8e4a511451d6d8a2290eec
Signed-off-by: Krishna Chaitanya Devarakonda <kdevarak@codeaurora.org>