usbmon: add bus number to text API

Due to a simple oversight when bus zero was added, the text API fails to
deliver the bus number in 'E' messages (which are equivalent of 'C'
messages, only for error case). This makes it harder, for instance,
use a search-and-highlight in a text editor. So fix it.

Also, Alan Stern requested adding timestamps to 'E' messages. This is
purely cosmetic, but makes it easier to read the trace. This is done
for both text and binary APIs.

Signed-off-by: Pete Zaitcev <zaitcev@redhat.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>