usb: ehci: fix comment for EHCI_SHRINK_JIFFIES

EHCI_SHRINK_JIFFIES should be 5ms, which was just used originally,
and not 200ms, so fix it.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>