greybus: interface_block: rename module.[c|h] to interface_block.[c|h]

"modules" in the driver model here, are really "interface blocks" as
that is what they are physically tied to.  So rename the files before we
start changing the code to make it obvious what is going on.

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