ARM: dts: msm: change emmc clock line drive strength

The clock line drive strength for eMMC should be 16 mA for msm8974pro-ab
mtp platform. If it is set to any other value for this platform, it can
lead to CRC errors.

Change-Id: I717c9b895d231148b4b9522b63fb3642c956bdf8
Signed-off-by: Krishna Konda <kkonda@codeaurora.org>