dt-bindings: platform: msm: Add DT bindings for GENI serial engine driver

Add DT bindings for GENI serial engine driver which provides
common functionality used by other serial bus drivers
such as I2c, SPI, UART), and does resource management for
those drivers.

Change-Id: I7b3572fcf42d95d57ec1dd452ab132c4a9032c53
Signed-off-by: Akash Asthana <akashast@codeaurora.org>