kbuild: do not add $(bounds-file) and $(offsets-file) to targets

$(always) is added to targets by scripts/Makefile.build.
Moreover, filechk does not need .*.cmd files.

Adding these two files to targets is redundant.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>