msm: iommu: Fix typo in driver probe function

After getting the alternate iface clock, the driver
checks the error on the alternate clock rather than
alternate iface clock. Fixed this typo.

Change-Id: If0275291cc48ecb5909ec6b91033d279365a24a4
Signed-off-by: Neeti Desai <neetid@codeaurora.org>