[SCSI] Allow nvram settings to determine bus mode

The PDC code can set the bus mode, but we were ignoring that setting.
Also move the code that determines bus mode into its own function.

Signed-off-by: Matthew Wilcox <matthew@wil.cx>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
1 file changed