usb: bam: associate usb_bam with the controller instead of the speed

Changes the usb_bam to be associated with the specific controller
that it is connected to in the hardware. This replaces the
existing paradigm where the association was made with prior
knowledge as to which controller can reach which speed (e.g. SSUSB_BAM).
This will allow supporting runtime LPM from the dwc3 controller, in
addition to the existing support for the CI controller.

Change-Id: I1fedda6d6e4605bf9444dc4833a51461875c669f
Signed-off-by: Dov Levenglick <dovl@codeaurora.org>
Signed-off-by: Maya Erez <merez@codeaurora.org>