usb: chipidea: remove unused field "regs" from ci13xxx

The old implementation used global hw_bank, the new implementation uses
udc-local hw_bank. This field seems to be a leftover from previous coding
experiments.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>