scripts: Remove export_report.pl

This script has been broken for 5 years with no user complaints.

It first had its .mod.c parser broken in commit a3d0cb04 ("modpost:
use __section in the output to *.mod.c"). Later, it had its object file
enumeration broken in commit f65a4868 ("kbuild: change module.order
to list *.o instead of *.ko"). Both of these changes sat for years with
no reports.

Rather than reviving this script as we make further changes to `.mod.c`,
this patch gets rid of it because it is clearly unused.

Signed-off-by: Matthew Maurer <mmaurer@google.com>
Acked-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>