Introduce function for_each_listed_submodule() and replace a loop
in module_init() with a call to it.
The new function will also be used in other parts of the
system in later patches.
Mentored-by: Christian Couder <christian.couder@gmail.com> Mentored-by: Stefan Beller <sbeller@google.com> Signed-off-by: Prathamesh Chavan <pc44800@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>