[SCSI] Change Kconfig option from IOMAPPED to MMIO

Most of the Kconfig options for switching between IO Port and MMIO
operations use the opposite sense from sym2.  Really, this option
should be set at a chipset level rather than per-driver.

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