msm: mhi_uci: Add support for platform devices

In order to support multiple instances of mhi_uci
net devices, add platform device support. Platform
specific information can be specified in the device
tree and used in the driver. Also create separate debug
log buffer per client to make debugging easier.

CRs-Fixed: 1086301
Change-Id: Ibfc9b7bb36e5d10a56c9b72494806419383b72f6
Signed-off-by: Sujeev Dias <sdias@codeaurora.org>