usb: chipidea: mark register map as "const" and convert to u8

This patch makes the controller register map ci_regs_nolpm and ci_regs_lpm as
"const". Further, as all offset fit into a single byte, the type is changed
from uintptr_t to u8.

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>