usb: misc: Add snapshot of diag_bridge driver

Add diag_bridge driver which is used to communicate with the diag
and QMI interfaces exposed by Qualcomm devices. This snapshot is
taken as of msm-3.10 'commit d722f698a54e ("regulator: core: Fix
buffer overflow issue")'.
Also rename the diag_bridge driver to diag_ipc_bridge.c.

Change-Id: Ide503c5bf729a7e41de98b12c89e4edc12af61fe
Signed-off-by: Ajay Agarwal <ajaya@codeaurora.org>