usb: common: create Kconfig file

Create Kconfig file for USB common core, and move USB_LED_TRIG
and USB_ULPI_BUS configs into the new file from the parent Kconfig,
it will help to add new configs later.

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Link: https://lore.kernel.org/r/1567070558-29417-10-git-send-email-chunfeng.yun@mediatek.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>