usb: gadget: Enable/Disable USB_BAM based on composition

BAM is used only in USB BAM mode. If platform has BAM enabled
by default in peripheral mode then it may slow down DDR access
by USB and also observing throughput degradation for software path
transfers. Since, USB legacy mode doesn't use BAM2BAM mode disable
the same for USB legacy mode and enable USB BAM based on composition.

Change-Id: I564caea896fb6b7b7acef12dc72e1bf179977b3f
Signed-off-by: Chandana Kishori Chiluveru <cchiluve@codeaurora.org>
Signed-off-by: Ajay Agarwal <ajaya@codeaurora.org>