iommu/msm: Fix error handling in msm_iommu_unmap()

Error handling in msm_iommu_unmap() is broken. On some error
conditions retval is set to a non-zero value which causes
the function to return 'len' at the end. This hides the
error from the user. Zero should be returned in those error
cases.

Cc: David Brown <davidb@codeaurora.org>
Cc: Stepan Moskovchenko <stepanm@codeaurora.org>
Cc: stable@vger.kernel.org # >= 3.1
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Acked-by: David Brown <davidb@codeaurora.org>

drivers/iommu/msm_iommu.c

@@ -482,23 +482,19 @@ static size_t msm_iommu_unmap(struct iommu_domain *domain, unsigned long va,
 
 	priv = domain->priv;
 
-	if (!priv) {
-		ret = -ENODEV;
+	if (!priv)
 		goto fail;
-	}
 
 	fl_table = priv->pgtable;
 
 	if (len != SZ_16M && len != SZ_1M &&
 	    len != SZ_64K && len != SZ_4K) {
 		pr_debug("Bad length: %d\n", len);
-		ret = -EINVAL;
 		goto fail;
 	}
 
 	if (!fl_table) {
 		pr_debug("Null page table\n");
-		ret = -EINVAL;
 		goto fail;
 	}
 
@@ -507,7 +503,6 @@ static size_t msm_iommu_unmap(struct iommu_domain *domain, unsigned long va,
 
 	if (*fl_pte == 0) {
 		pr_debug("First level PTE is 0\n");
-		ret = -ENODEV;
 		goto fail;
 	}