scsi: delete the MCA specific drivers and driver code

The support for CONFIG_MCA is being removed, since the 20
year old hardware simply isn't capable of meeting today's
software demands on CPU and memory resources.

This commit removes the MCA specific SCSI drivers, and the
MCA specific portions of code in dual role ISA/MCA drivers.
Also, the MCA specific SCSI documentation is removed.

Cc: James Bottomley <JBottomley@parallels.com>
Cc: linux-scsi@vger.kernel.org
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>