ARM: dts: msm: Add Incall recording support in APQ8084

APQ8084 uses external modem for voice calls and is communicated
with modem through slimbus. Add slimbus6 logical port to support
in-call record.

Change-Id: I8ac3ed12e5b608eb1323de27941deada4a5b907e
Signed-off-by: Vidyakumar Athota <vathota@codeaurora.org>