Prevent a race condition upon resume by adding a supplementary delay.

Prevent a race condition upon resume by adding a supplementary delay.

This is a workaround needed at least by Renesas controllers.  I didn't
find any documentation about this issue and I guess other open source
xHCI implementations do not see this race because they do much more work
upon resume.

Thanks to Remi Locherer for reporting this issue on bugs@.