usb: chipidea: fix and improve dependencies if usb host or gadget support is built as module

Since commit "5e0aa49e usb: chipidea: use generic map/unmap routines",
the udc part of the chipidea driver needs the generic usb gadget helper
functions. If the chipidea driver with udc support is built into the
kernel and usb gadget is built a module, the linking of the kernel
fails with:

drivers/built-in.o: In function `_hardware_dequeue':
drivers/usb/chipidea/udc.c:527:
    undefined reference to `usb_gadget_unmap_request'
drivers/usb/chipidea/udc.c:1269:
    undefined reference to `usb_gadget_unmap_request'
drivers/usb/chipidea/udc.c:1821:
    undefined reference to `usb_del_gadget_udc'
drivers/usb/chipidea/udc.c:443:
    undefined reference to `usb_gadget_map_request'
drivers/usb/chipidea/udc.c:1774:
    undefined reference to `usb_add_gadget_udc'

This patch changes the dependencies, so that udc support can only be
activated if the linux gadget support (USB_GADGET) is builtin or both
chipidea driver and USB_GADGET are modular. Same dependencies for the
chipidea host support and the linux host side USB support (USB).

While there, fix the indention of chipidea the help text.

Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Reviewed-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>