usb: mdm_bridge: Fix compilation error

Driver is using err macro which is removed from usb.h
in msm-3.10 kernel. Hence replace this macro with pr_err.

Change-Id: If675c684e061a8b43fc304a2326cfe36b5fbc5d1
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>