usb: bam: Only call msm_hw_disable_bam for CI controller

The msm_hw_disable_bam() function may be defined if
CONFIG_USB_CI13XXX_MSM is enabled, but it is invalid to
call it if the USB 2.0 controller is not actually prsent
or enabled. Make sure to call it only if USB BAM is known
to be set up for the CI_CTRL bam type.

Also hide its usage in the gadget drivers by abstracting the
calls within the usb_bam_a2_reset() function.

Change-Id: Ie6633ec8c40367fadeeafba2f009b0bfad3c229e
Signed-off-by: Jack Pham <jackp@codeaurora.org>