msm: mdss: Read the bridge chip name and instance id from DTSI

As different targets might have different bridge chips connected
to the DSI interfaces, we need to read the bridge chip name and
instance id from the dtsi nodes instead of hardcoding it in.

Change-Id: Ic37fb3fa4777803648a17211b7ffb153d780bd76
Signed-off-by: Siddharth Zaveri <szaveri@codeaurora.org>