ARM: dts: msm: update hx8394a's gamma setting

Update hx8394a's initialization sequence, which modifies
its gamma value to standard 2.2. We need tuning panel gamma
to 2.2 as per display standard, this is panel specific
optimization that comes from vendor

Change-Id: I83240eee35b036090c785126c3a70f1dd214fd62
Signed-off-by: rayz <rayzhang@codeaurora.org>