ARM: dts: msm: decrease skug I2C-5 bus speed

Focaltech FT53x6 touchscreen IC may reports fake touch event when
it runs on high I2C bus speed. Decrease skug touchscreen I2C bus
speed to prevent this issue.

Change-Id: I4549b25a80bd3c2a08f2b112430659a00c83d271
Signed-off-by: Bingzhe Cai <bingzhec@codeaurora.org>