usb: chipidea: debug: fix sparse non static symbol warnings

Fixes the following sparse warnings:

drivers/usb/chipidea/debug.c:211:5: warning:
 symbol 'ci_otg_show' was not declared. Should it be static?
drivers/usb/chipidea/debug.c:334:5: warning:
 symbol 'ci_registers_show' was not declared. Should it be static?

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Peter Chen <peter.chen@freescale.com>