USB: gadget: Replace USB_GADGET_XPORT_BAM with BAM2BAM/BAM_DMUX

USB_GADGET_XPORT_BAM was historically used for BAM_DMUX mode but
later QDSS started using it for BAM2BAM between USB and QDSS.
In fact there is another transport type - USB_GADGET_XPORT_BAM2BAM
which is exactly for this and used for A2 <--> USB BAM2BAM mode.
This further gets complicated with the addition of new transport
type - USB_GADGET_XPORT_BAM_DMUX and userspace specifying bam and
bam_dmux xport_type with QDSS for bam2bam and bam_dmux mode (DPL)
but it passes bam as rmnet xport_type for bam_dmux.
Part one of cleanup involves this patch which replaces usage of
USB_GADGET_XPORT_BAM with USB_GADGET_XPORT_BAM2BAM or
USB_GADGET_XPORT_BAM_DMUX (over-ride for rmnet) in the drivers.
Part two will update userspace code to pass bam_dmux as rmnet
xport_type instead of bam and explicit bam2bam for qdss xport_type.
Until this happens override bam xport to bam_dmux/bam2bam for rmnet
and qdss to maintain userspace ABI compatibility.

Change-Id: Iee896b6ed9e08321f29561c56a2c647472da5647
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>
Signed-off-by: Tarun Gupta <tarung@codeaurora.org>