kbuild: fix typos "prequisites" to "prerequisites"

This typo in scripts/Makefile.build has been present for more than 20
years. It was accidentally copy-pasted to other scripts/Makefile.* files.
Fix them all.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>