[SCSI] fix bio.bi_rw handling

Return of the bi_rw tests is no longer bool after commit 74450be1. So
testing against constants doesn't make sense anymore. Fix this bug in
osd_req_read by removing "== 1" in test.

This is not a problem now, where REQ_WRITE is 1, but this can change
in the future and we don't want to rely on that.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>