The way we enable ULPI support today isn't something that should work.
The "optional" keyword in a choice statement is not a documented
feature. To make this work in a supported way, make USB_ULPI something
we ask about if USB_HOST is set. Next, we move the choice of what
viewer to use to be after the framework portion and to depend on that.
We then borrow a few words from the top-level README to make the help
text here clearer. Finally we make the Qualcomm driver select ULPI as
it's required and we make the tegra driver not duplicate a check that
Kconfig now handles for us.

Signed-off-by: Tom Rini <trini@konsulko.com>

The last platform to enable this driver was removed in 2019. Remove this
unused code and documentation now.

Signed-off-by: Tom Rini <trini@konsulko.com>

'default' on a choice refers to the symbol selected by default, not to
the choice mode, so 'default n' is meaningless.

No functional changes. Optional choices implicitly default to n mode
(and there is no way to make them default to another mode).

Discovered in Kconfiglib (https://github.com/ulfalizer/Kconfiglib),
which prints the following warning:

	warning: the default selection n (undefined) of <choice> (defined at drivers/usb/ulpi/Kconfig:3) is not contained in the choice

I've added a corresponding warning to the C tools too, which is
currently in linux-next: https://patchwork.kernel.org/patch/9983667/

Signed-off-by: Ulf Magnusson <ulfalizer@gmail.com>

The following options can be now enabled via defconfig:
- CONFIG_USB_ULPI
- CONFIG_USB_ULPI_VIEWPORT
- CONFIG_USB_ULPI_VIEWPORT_OMAP

Signed-off-by: Mateusz Kulikowski <mateusz.kulikowski@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Acked-by: Marek Vasut <marex@denx.de>