kbuild: remove scripts/basic/% build target

This build rule was introduced by commit cd05e6bd

 ("[PATCH]
kbuild: fix split-include dependency") to handle the dependency of
scripts/basic/split-include.

Now, fixdep is the only tool in scripts/basic/, and this rule is
no longer used.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>