ARM: dts: msm: Remove I/O coherence for the GPU

I/O coherence has some limitations that make it less preferable than
the usermode cache operations.  Given these limitations the user mode
driver teams have requested that I/O coherence be disabled.

Change-Id: Ic0dedbadbc10b3a6239e20df8b527a5738a1a3a4
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>