ARM: dts: msm: Disable io-coherency for GSI on SM6150

Disable io-coherency when allocating buffers for GSI in usb
driver to avoid SMMU faults.

Change-Id: I12858a36dfa51886078f3c60b719ab34b9435f70
Signed-off-by: Pratham Pratap <prathampratap@codeaurora.org>