kmod: ptest fixes

kmod: ptest fixes

 Make kmod-ptest able to compile with separated source and
 build dir. Since kmod test files contain kernel modules for
 many different architectures, strip and arch gets confused
 and throws errors.

Signed-off-by: Tudor Florea <tudor.florea@enea.com>
Signed-off-by: Björn Stenberg <bjst@enea.com>
Signed-off-by: Maxin B. John <maxin.john@enea.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>