usb: usb_bam: disable BAM before reset BAM pipes

Resetting the BAM pipes is allowed only if the USB HW core is switch from
BAM mode to Legacy mode. So the USB HW core is de-attached from its BAM
until the BAM reset is completed.

Lack of this setting to the USB HW core may result in halted core.

Change-Id: I8ef69ccdb8a8b926e428829a42764332263ba6f3
CRs-Fixed: 526649
Signed-off-by: Ido Shayevitz <idos@codeaurora.org>