greybus: interface_block: rename the sysfs files to not have 'module' in them

The sysfs files for an interface block should not have 'module' in them.
This was a hold-over from when we thought we were going to have
all attributes of a "module" in one directory.  Remove the prefix as
it's not needed, and is confusing considering modules can not have
strings or any of these attributes.

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