Some XHCI hardware requires dropping the endpoint context before
adding it again.

MFC after:	3 days
Submitted by:	Kohji Okuno <okuno.kohji@jp.panasonic.com>


git-svn-id: svn+ssh://svn.freebsd.org/base/head@271953 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f