ab8500-charger: Add AB8505_USB_LINK_STATUS

The AB8505 does not have the same address for USB link-status
as has ab8500. Add AB8505_USB_LINK_STATUS and code to switch
to correct constant.

Signed-off-by: Hakan Berg <hakan.berg@stericsson.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Mian Yousaf KAUKAB <mian.yousaf.kaukab@stericsson.com>
Reviewed-by: Marcus COOPER <marcus.xm.cooper@stericsson.com>
Reviewed-by: Rabin VINCENT <rabin.vincent@stericsson.com>