usb: gadget: Add snapshot of USB BAM DMUX driver

This change adds USB BAM DMUX driver which is required by RmNET
and DPL functions to work in SW mode.

This snapshot is taken as of msm-3.18 'commit 4a06b0168aeb ("ANDROID:
sdcardfs: Make WARN_RATELIMIT to pr_debug")'.

This change also fixes the coding style errors.

Change-Id: Ie565a3354765a1d042182cfcd9f9812225a0d2f7
Signed-off-by: Ajay Agarwal <ajaya@codeaurora.org>