[ARM] rpc: acornscsi: fixup abort/reset methods, fix build errors

Revive the AcornSCSI driver, update it for the replacement command
abort and host reset methods, and fix the build errors in
acornscsi-io.S.

Acked-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>