ARM: dts: msm: Add LDO_6 to supply vdd for io-expander on MSM8917 CDP

Add pm8917_l6 VREG which supplies vdd for io-expander on 8017.
Without this i2c communication fails on i2c-4 with other slaves
as well due to io-expander pulling i2c lines low if VDD not ON.

CRs-Fixed: 2053404
Change-Id: Ide2113fff7e6d7cab5074974d7578328227b4408
Signed-off-by: Arumuga Durai A <cadurai@codeaurora.org>