[SCSI] ch: remove forward declarations

This moves ch_template and changer_fops structs to the end of file and
removes forward declarations.

This also removes some trailing whitespace.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>