ide-cd: move request prep chunk from cdrom_do_newpc_cont to rq issue path

As a nice side effect, this minimizes the IRQ handler execution time.

There should be no functionality change resulting from this patch.

[bart: remove extra newlines from ide_cd_do_request()]

Signed-off-by: Borislav Petkov <petkovbb@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>