[SCSI] st: log message changes

Printk -> sdev_printk change originally from Luben Tuikov
<ltuikov@yahoo.com>. Loglevel changes prompted by Matthew Wilcox
<matthew@wil.cx>.

Signed-off-by: Kai Makisara <kai.makisara@kolumbus.fi>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>