greybus: protocol: name protocols.

We want to be able to "blame" a protocol for things at times, so give
them a name we can refer to them by.  Announce when they are added or
removed from the system so we have a chance to know what is going on
in the kernel logs.

Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>
Reviewed-by: Alex Elder <elder@linaro.org>