kbuild: do not deduplicate modules.order
The AWK code was added to deduplicate modules.order in case $(obj-m)
contains the same module multiple times, but it is actually unneeded
since commit
b2c885549122 ("kbuild: update modules.order only when
contained modules are updated").
The list is already deduplicated before being processed by AWK because
$^ is the deduplicated list of prerequisites.
(Please note the real-prereqs macro uses $^)
Yet, modules.order will contain duplication if two different Makefiles
build the same module:
foo/Makefile:
obj-m += bar/baz.o
foo/bar/Makefile:
obj-m += baz.o
However, the parallel builds cannot properly handle this case in the
first place. So, it is better to let it fail (as already done by
scripts/modules-check.sh).
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>