USB: mxc: gadget: remove 60mhz clock requirement for freescale mx51 usb core

renamed fsl_mx3_udc.c -> fsl_mxc_udc.c
for mx51, usb core is clocked from sources that are not 60mhz.

Signed-off-by: Dinh Nguyen <Dinh.Nguyen@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>