interface: we really are creating/destroying interfaces not modules.

rename gb_add_module     -> gb_add_interface
rename gb_remove_modules -> gb_remove_interfaces
rename gb_remove_module  -> gb_remove_interface

And move the function prototypes to interface.h, where they belong.

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

This is really a list of interfaces, not modules, so rename it so that
we don't get confused when we really do add modules to the whole system
later on.

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

It's a local interface lock, not a modules lock, so rename it.

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