USB: change maintainership of ohci-hcd and ehci-hcd

Following the loss of David Brownell, I volunteer to maintain the
ohci-hcd and ehci-hcd drivers.  This patch (as1472) makes it official.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>