kernel: include built-in module list

kernel: include built-in module list

Add modules.builtin to the kernel package for improved handling of loadable
and builtin modules. As with other distros, this allows 'modprobe <module>'
to consistently return success for both loaded/built-in modules, a useful
feature for presence-testing.

Given OpenWrt's few built-in modules, this change and related kmodloader
support add ~1 KB to the compressed image size.

Using sch_fq_codel (builtin) and sch_cake (loadable) for example:

     root@OpenWrt:/# modprobe sch_fq_codel && echo SUCCESS || echo FAIL
     SUCCESS
     root@OpenWrt:/# modprobe sch_cake && echo SUCCESS || echo FAIL
     SUCCESS

     root@OpenWrt:/# rmmod sch_fq_codel
     module is builtin

Signed-off-by: Tony Ambardar <itugrok@yahoo.com>