usb: chipidea: Properly mark little endian descriptors

The DMA descriptors are little endian, and we do a pretty good
job of handling them with the proper le32_to_cpu() markings, but
we don't actually mark them as __le32. This means checkers like
sparse can't easily find new bugs. Let's mark the members of
structures properly and fix the few places where we're missing
conversions.

Cc: Peter Chen <peter.chen@nxp.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stephen Boyd <stephen.boyd@linaro.org>
Signed-off-by: Peter Chen <peter.chen@nxp.com>