ARM: dts: msm: Configure BLSP6-UART6 for MSM8953

Configure BLSP2 UART6 instance for MSM8953 with default
status set to disabled.
Client needs to enable this instance as per usecase.
UART6 is exposed on pins 19-22 of the sensor connector (J53)
of the Open-Q board.

Change-Id: I142ab1ef348f98b17ecfbbbeed3ba57dd4285a22
Signed-off-by: c_vnerel <venkataraman.nerellapalli@codeaurora.org>