msm: usb_bam: choose dynamically between usb and hsic bam

This change allows to change between a usb and hsic via sysfs
interface. This allows the same image to support both flavors and
pass between them upon sysfs change and reboot.

Change-Id: I94640c0ed7f0af9a882a20de60ad44288abe8141
Signed-off-by: Lena Salman <esalman@codeaurora.org>