fsl_usb2_udc: Rename the arguments of the fsl_writel macro.

Rename the arguments of the fsl_writel macro to match their use.
Remove a couple of unnecessary prototypes.

Signed-off-by: Will Newton <will.newton@gmail.com>
Acked-by: Li Yang <leoli@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>