ARM: dts: msm: update hx8394f's gamma setting

Update hx8394f'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: I1c032b39cff20c8f7741a8da0e9a2f3aeb1520dd
Signed-off-by: Ray Zhang <rayz@codeaurora.org>