staging: atomisp: fix build breakage from files going away

Previous patches deleted files, but the Makefile still referenced their
.o files.  Fix this up by removing them in the Makefile.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>