msm_fb: Remove the extra freelist in display_commit

There is an extra freelist call to unmap IOMMU source buffers
in display_commit for LCDC interface. This is causing IOMMU
page faults during boot up on targets with LCDC interfaces.
Remove this extra freelist call.

Change-Id: I12a905efc82c5b9751acbc5941a66d0b58027509
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>