Revert "USB: chipidea: add vbus detect for udc"

There are several problems with this patch:
  + in introduces a sparse warning for a condition that's always negative,
  + and because of that, it actually doesn't do anything useful,
  + and vbus detection belongs to otg, not device function anyway.

This reverts commit 8c4fc031.

Signed-off-by: Peter Chen <peter.chen@freescale.com>
[Alex: amended the above text]
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>