usb: fsl: Rename fdt_fixup_dr_usb

The function fdt_fixup_dr_usb is specific to fsl/nxp. So,
make the function name explicit and rename fdt_fixup_dr_usb
into fsl_fdt_fixup_dr_usb.

Signed-off-by: Sriram Dash <sriram.dash@nxp.com>