greybus: isolate greybus module code

greybus: isolate greybus module code

Define new source files "module.h" and "module.c" to separate the
definitions of the Greybus module abstraction from other code.

Rename "greybus_module" to be "gb_module", for brevity.  Do the same
for a few other symbols with "greybus_module" in their names.  A few
(like greybus_module_id) are more visible outside this kernel module
so we'll keep their names more descriptive.

Add a definition for U8_MAX in "kernel_ver.h" (it appeared in 3.14).

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