ide: remove ide_do_drive_cmd()

* Use elv_add_request() instead of __elv_add_request() in ide_do_drive_cmd().

* ide_do_drive_cmd() is used only in ide-{atapi,cd}.c so inline it there.

There should be no functional changes caused by this patch.

Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>