iommu: Fix __msm_map_iommu_common()

When msm_iommu_meta_create() returns error, msm_iommu_map_mutex is not
getting unlocked and error pointer is being passed to
msm_iommu_meta_put(). Fix this.

CRs-Fixed: 803179
Change-Id: I7c1c615bc697693b2036351340065af3f080ed63
Signed-off-by: Neha Atri <natri@codeaurora.org>