skd: remove SKD_OMIT_FROM_SRC_DIST ifdefs

SKD_OMIT_FROM_SRC_DIST is never defined.

Cc: Akhil Bhansali <abhansali@stec-inc.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>