ARC relocatable object files contain one/more .gnu.linkonce.arcextmap.*
sections (collated by kernel/vmlinux.lds into .arcextmap in final link).
This section is used by debuggers to display the extension instructions
and need-not be loaded by target (hence !SHF_ALLOC)

The final kernel binary only needs .arcextmap entry in modpost's ignore
list (section_white_list[]). However when building modules, modpost scans
each object file individually, hence tripping on non-aggregated
.gnu.linkonce.arcextmap.* entries as well.

Thus need for the 2 entires !
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>
Acked-by: NSam Ravnborg <sam@ravnborg.org>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>