USB: Chipidea: rename struct ci13xxx variables from udc to ci

struct ci13xxx represent the controller, which may be device or host,
so name its variables as ci.

Signed-off-by: Richard Zhao <richard.zhao@freescale.com>
Reviewed-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>